diff --git a/pkg/analysis_server/lib/src/services/correction/assist_internal.dart b/pkg/analysis_server/lib/src/services/correction/assist_internal.dart
index 86b9084..0f9124d 100644
--- a/pkg/analysis_server/lib/src/services/correction/assist_internal.dart
+++ b/pkg/analysis_server/lib/src/services/correction/assist_internal.dart
@@ -220,7 +220,7 @@
     }
     _configureTargetLocation(node);
 
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     bool validChange = true;
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       Token keyword = declaredIdentifier.keyword;
@@ -270,7 +270,7 @@
     // prepare type source
     _configureTargetLocation(node);
 
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     bool validChange = true;
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       builder.addInsertion(name.offset, (DartEditBuilder builder) {
@@ -326,7 +326,7 @@
     }
     _configureTargetLocation(node);
 
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     bool validChange = true;
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       Token keyword = declarationList.keyword;
@@ -386,7 +386,7 @@
         getVariableNameSuggestionsForExpression(type, expression, excluded);
 
     if (suggestions.isNotEmpty) {
-      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+      var changeBuilder = _newDartChangeBuilder();
       await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
         builder.addInsertion(offset, (DartEditBuilder builder) {
           builder.write('var ');
@@ -439,7 +439,7 @@
     }
     interfaces.addAll(classElement.interfaces);
 
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       builder.addReplacement(
           range.startStart(
@@ -473,7 +473,7 @@
     }
     String prefix = utils.getNodePrefix(comment);
 
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       builder.addReplacement(range.node(comment), (DartEditBuilder builder) {
         builder.writeln('/**');
@@ -543,7 +543,7 @@
       }
     }
 
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       builder.addReplacement(range.node(comment), (DartEditBuilder builder) {
         for (String newLine in newLines) {
@@ -617,7 +617,7 @@
       code += ';';
       SourceRange replacementRange =
           range.startEnd(getter.returnType ?? getter.propertyKeyword, getter);
-      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+      var changeBuilder = _newDartChangeBuilder();
       await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
         builder.addSimpleReplacement(replacementRange, code);
       });
@@ -670,7 +670,7 @@
     code += ';';
     SourceRange replacementRange =
         range.startEnd(fieldList.keyword, fieldDeclaration);
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       builder.addSimpleReplacement(replacementRange, code);
     });
@@ -689,7 +689,7 @@
     String relativePath = relative(libraryPath, from: dirname(partPath));
     String uri = new Uri.file(relativePath).toString();
     SourceRange replacementRange = range.node(directive.libraryName);
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       builder.addSimpleReplacement(replacementRange, "'$uri'");
     });
@@ -721,7 +721,7 @@
       return;
     }
 
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       builder.convertFunctionFromSyncToAsync(body, typeProvider);
     });
@@ -754,7 +754,7 @@
     String prefix = utils.getNodePrefix(body.parent);
     String indent = utils.getIndent(1);
 
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       builder.addReplacement(range.node(body), (DartEditBuilder builder) {
         if (body.isAsynchronous) {
@@ -815,7 +815,7 @@
       return;
     }
 
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       builder.addReplacement(range.node(body), (DartEditBuilder builder) {
         if (body.isAsynchronous) {
@@ -903,7 +903,7 @@
       }
       String fieldName = parameterInitializer.fieldName.name;
 
-      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+      var changeBuilder = _newDartChangeBuilder();
       await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
         // replace parameter
         builder.addSimpleReplacement(range.node(parameter), 'this.$fieldName');
@@ -995,7 +995,7 @@
     String indent = utils.getIndent(1);
     int firstBlockLine = utils.getLineContentEnd(body.leftBracket.end);
     // add change
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       // TODO(brianwilkerson) Create linked positions for the loop variable.
       builder.addSimpleReplacement(
@@ -1044,7 +1044,7 @@
       return;
     }
 
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       builder.addReplacement(new SourceRange(literal.offset, literal.length),
           (DartEditBuilder builder) {
@@ -1091,7 +1091,7 @@
       return;
     }
 
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       if (getExpressionParentPrecedence(prefExpression) >=
           TokenClass.RELATIONAL_OPERATOR.precedence) {
@@ -1145,7 +1145,7 @@
       return;
     }
 
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       if (getExpressionParentPrecedence(prefExpression) >=
           TokenClass.RELATIONAL_OPERATOR.precedence) {
@@ -1214,7 +1214,7 @@
       return;
     }
 
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       builder.addDeletion(
           range.startStart(prefixExpression, prefixExpression.operand));
@@ -1239,7 +1239,7 @@
       // prepare type
       DartType type = parameterElement.type;
 
-      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+      var changeBuilder = _newDartChangeBuilder();
       await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
         // replace parameter
         if (type.isDynamic) {
@@ -1317,7 +1317,7 @@
       _coverageMarker();
       return;
     }
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       // rename field
       builder.addSimpleReplacement(range.node(nameNode), '_$name');
@@ -1417,7 +1417,7 @@
     } else if (operatorType == TokenType.GT_EQ) {
       newOperator = '<=';
     }
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       builder.addSimpleReplacement(leftRange, _getRangeText(rightRange));
       builder.addSimpleReplacement(rightRange, _getRangeText(leftRange));
@@ -1451,7 +1451,7 @@
       }
     }
 
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       _convertFlutterChildToChildren(namedExp, eol, utils.getNodeText,
           utils.getLinePrefix, utils.getIndent, utils.getText, builder);
@@ -1599,7 +1599,7 @@
     }
     var stateType = stateClass.type.instantiate([widgetClassElement.type]);
 
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       builder.addReplacement(range.node(superclass), (builder) {
         builder.writeType(statefulWidgetClass.type);
@@ -1709,7 +1709,7 @@
       List<Expression> parentElements = parentList.elements;
       int index = parentElements.indexOf(widget);
       if (index != parentElements.length - 1) {
-        DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+        var changeBuilder = _newDartChangeBuilder();
         await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
           Expression nextWidget = parentElements[index + 1];
           var nextRange = range.node(nextWidget);
@@ -1743,7 +1743,7 @@
       List<Expression> parentElements = parentList.elements;
       int index = parentElements.indexOf(widget);
       if (index > 0) {
-        DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+        var changeBuilder = _newDartChangeBuilder();
         await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
           Expression previousWidget = parentElements[index - 1];
           var previousRange = range.node(previousWidget);
@@ -1790,7 +1790,7 @@
       return;
     }
 
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       var firstChild = childrenExpressions.first;
       var lastChild = childrenExpressions.last;
@@ -1818,7 +1818,7 @@
 
     // child: new ThisWidget(child: ourChild)
     // children: [foo, new ThisWidget(child: ourChild), bar]
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       var childExpression = childArgument.expression;
       var childText = utils.getNodeText(childExpression);
@@ -1890,7 +1890,7 @@
       return;
     }
 
-    var changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (builder) {
       builder.addReplacement(range.node(widgetExpr), (builder) {
         builder.writeType(streamBuilderElement.type);
@@ -1984,7 +1984,7 @@
       }
     }
 
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       builder.addReplacement(range.node(widgetExpr), (DartEditBuilder builder) {
         if (parentClassElement == null) {
@@ -2066,7 +2066,7 @@
         return;
       }
 
-      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+      var changeBuilder = _newDartChangeBuilder();
       await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
         builder.addReplacement(selectedRange, (DartEditBuilder builder) {
           builder.writeType(parentClassElement.type);
@@ -2148,7 +2148,7 @@
       _coverageMarker();
       return;
     }
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       String showCombinator = ' show ${referencedNames.join(', ')}';
       builder.addSimpleInsertion(importDirective.end - 1, showCombinator);
@@ -2209,7 +2209,7 @@
         getVariableNameSuggestionsForExpression(castType, null, excluded);
 
     if (suggestions.isNotEmpty) {
-      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+      var changeBuilder = _newDartChangeBuilder();
       await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
         builder.addInsertion(offset, (DartEditBuilder builder) {
           builder.write(eol + prefix + statementPrefix);
@@ -2248,7 +2248,7 @@
     String thenSource = _getNodeText(thenStatement);
     String elseSource = _getNodeText(elseStatement);
 
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       builder.addSimpleReplacement(range.node(condition), invertedCondition);
       builder.addSimpleReplacement(range.node(thenStatement), elseSource);
@@ -2311,7 +2311,7 @@
     String oldSource = utils.getRangeText(lineRanges);
     String newSource = utils.indentSourceLeftRight(oldSource);
 
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       builder.addSimpleReplacement(range.node(targetIfStatement),
           'if ($condition) {$eol$newSource$prefix}');
@@ -2377,7 +2377,7 @@
     String oldSource = utils.getRangeText(lineRanges);
     String newSource = utils.indentSourceLeftRight(oldSource);
 
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       builder.addSimpleReplacement(range.node(outerIfStatement),
           'if ($condition) {$eol$newSource$prefix}');
@@ -2454,7 +2454,7 @@
       return;
     }
 
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       builder.addSimpleReplacement(
           range.endStart(declNode, assignExpression.operator), ' ');
@@ -2524,7 +2524,7 @@
       return;
     }
 
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       builder.addSimpleReplacement(
           range.endStart(decl.name, assignExpression.operator), ' ');
@@ -2567,7 +2567,7 @@
       return;
     }
     Token keyword = declarationList.keyword;
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       SourceRange typeRange = range.startStart(typeNode, firstVariable);
       if (keyword != null && keyword.lexeme != 'var') {
@@ -2601,7 +2601,7 @@
     String indentArg = '$indentOld${utils.getIndent(1)}';
     String indentList = '$indentOld${utils.getIndent(2)}';
 
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       builder.addReplacement(range.node(node), (DartEditBuilder builder) {
         builder.write('[');
@@ -2679,7 +2679,7 @@
     String prefix = utils.getNodePrefix(statement);
 
     if (inVariable || inAssignment || inReturn) {
-      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+      var changeBuilder = _newDartChangeBuilder();
       await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
         // Type v = Conditional;
         if (inVariable) {
@@ -2770,7 +2770,7 @@
     }
 
     if (hasReturnStatements || hasExpressionStatements) {
-      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+      var changeBuilder = _newDartChangeBuilder();
       await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
         // returns
         if (hasReturnStatements) {
@@ -2856,7 +2856,7 @@
       rightConditionSource = _getRangeText(rightConditionRange);
     }
 
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       // remove "&& rightCondition"
       builder
@@ -2919,7 +2919,7 @@
       _coverageMarker();
       return;
     }
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       // remove initializer value
       builder.addDeletion(range.endStart(variable.name, statement.semicolon));
@@ -2970,7 +2970,7 @@
         utils.replaceSourceRangeIndent(statementsRange, indentOld, indentNew);
     // "block"
     {
-      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+      var changeBuilder = _newDartChangeBuilder();
       await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
         builder.addSimpleInsertion(statementsRange.offset, '$indentOld{$eol');
         builder.addSimpleReplacement(
@@ -2983,7 +2983,7 @@
     }
     // "if"
     {
-      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+      var changeBuilder = _newDartChangeBuilder();
       await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
         builder.addReplacement(statementsRange, (DartEditBuilder builder) {
           builder.write(indentOld);
@@ -3002,7 +3002,7 @@
     }
     // "while"
     {
-      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+      var changeBuilder = _newDartChangeBuilder();
       await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
         builder.addReplacement(statementsRange, (DartEditBuilder builder) {
           builder.write(indentOld);
@@ -3021,7 +3021,7 @@
     }
     // "for-in"
     {
-      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+      var changeBuilder = _newDartChangeBuilder();
       await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
         builder.addReplacement(statementsRange, (DartEditBuilder builder) {
           builder.write(indentOld);
@@ -3042,7 +3042,7 @@
     }
     // "for"
     {
-      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+      var changeBuilder = _newDartChangeBuilder();
       await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
         builder.addReplacement(statementsRange, (DartEditBuilder builder) {
           builder.write(indentOld);
@@ -3067,7 +3067,7 @@
     }
     // "do-while"
     {
-      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+      var changeBuilder = _newDartChangeBuilder();
       await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
         builder.addReplacement(statementsRange, (DartEditBuilder builder) {
           builder.write(indentOld);
@@ -3087,7 +3087,7 @@
     }
     // "try-catch"
     {
-      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+      var changeBuilder = _newDartChangeBuilder();
       await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
         builder.addReplacement(statementsRange, (DartEditBuilder builder) {
           builder.write(indentOld);
@@ -3117,7 +3117,7 @@
     }
     // "try-finally"
     {
-      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+      var changeBuilder = _newDartChangeBuilder();
       await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
         builder.addReplacement(statementsRange, (DartEditBuilder builder) {
           builder.write(indentOld);
@@ -3243,7 +3243,7 @@
       replacement = '$functionName = $returnType Function$parameters';
     }
     // add change
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       builder.addSimpleReplacement(
           range.startStart(node.typedefKeyword.next, node.semicolon),
@@ -3274,7 +3274,7 @@
       replacement = '$returnType Function$parameters $functionName';
     }
     // add change
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       builder.addSimpleReplacement(range.node(node), replacement);
     });
@@ -3294,7 +3294,7 @@
         int quoteLength = literal.isMultiline ? 3 : 1;
         String lexeme = literal.literal.lexeme;
         if (lexeme.indexOf(newQuote) < 0) {
-          DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+          var changeBuilder = _newDartChangeBuilder();
           await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
             builder.addSimpleReplacement(
                 new SourceRange(
@@ -3324,7 +3324,7 @@
             }
           }
         }
-        DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+        var changeBuilder = _newDartChangeBuilder();
         await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
           builder.addSimpleReplacement(
               new SourceRange(
@@ -3352,6 +3352,11 @@
     return utils.getRangeText(range);
   }
 
+  DartChangeBuilder _newDartChangeBuilder() {
+    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    return changeBuilder;
+  }
+
   bool _setupCompute() {
     var locator = new NodeLocator(selectionOffset, selectionEnd);
     node = locator.searchWithin(context.resolveResult.unit);
@@ -3368,7 +3373,7 @@
       return;
     }
 
-    var changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (builder) {
       builder.addReplacement(range.node(parent), (builder) {
         var childArgs = child.argumentList;
diff --git a/pkg/analysis_server/lib/src/services/correction/fix_internal.dart b/pkg/analysis_server/lib/src/services/correction/fix_internal.dart
index b10a98d..55c429c 100644
--- a/pkg/analysis_server/lib/src/services/correction/fix_internal.dart
+++ b/pkg/analysis_server/lib/src/services/correction/fix_internal.dart
@@ -569,7 +569,7 @@
     FunctionBody body = node.thisOrAncestorOfType<FunctionBody>();
     if (body != null && body.keyword == null) {
       TypeProvider typeProvider = this.typeProvider;
-      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+      var changeBuilder = _newDartChangeBuilder();
       await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
         builder.convertFunctionFromSyncToAsync(body, typeProvider);
       });
@@ -622,7 +622,7 @@
         // `cast` invocation.
         return;
       }
-      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+      var changeBuilder = _newDartChangeBuilder();
       await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
         if (needsParentheses) {
           builder.addSimpleInsertion(target.offset, '(');
@@ -643,7 +643,7 @@
         // `cast` invocation.
         return;
       }
-      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+      var changeBuilder = _newDartChangeBuilder();
       await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
         if (needsParentheses) {
           builder.addSimpleInsertion(target.offset, '(');
@@ -661,7 +661,7 @@
       });
       _addFixFromBuilder(changeBuilder, DartFixKind.ADD_EXPLICIT_CAST);
     } else {
-      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+      var changeBuilder = _newDartChangeBuilder();
       await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
         if (needsParentheses) {
           builder.addSimpleInsertion(target.offset, '(');
@@ -715,7 +715,7 @@
       // TODO(brianwilkerson) Determine whether this await is necessary.
       await null;
       if (offset != null) {
-        var changeBuilder = new DartChangeBuilder(session);
+        var changeBuilder = _newDartChangeBuilder();
         await changeBuilder.addFileEdit(context.file, (builder) {
           builder.addInsertion(offset, (builder) {
             builder.write(prefix);
@@ -770,7 +770,7 @@
       // TODO(brianwilkerson) Determine whether this await is necessary.
       await null;
       if (offset != null) {
-        var changeBuilder = new DartChangeBuilder(session);
+        var changeBuilder = _newDartChangeBuilder();
         await changeBuilder.addFileEdit(context.file, (builder) {
           builder.addInsertion(offset, (builder) {
             builder.write(prefix);
@@ -860,7 +860,7 @@
         hasTrailingComma = lastArgument.endToken.next.type == TokenType.COMMA;
       }
 
-      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+      var changeBuilder = _newDartChangeBuilder();
       await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
         builder.addInsertion(offset, (DartEditBuilder builder) {
           if (arguments.isNotEmpty) {
@@ -899,7 +899,7 @@
 
     Position exitPosition = new Position(file, token.offset - 1);
     String indent = utils.getIndent(1);
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       builder.addSimpleReplacement(
           range.startLength(token, 0), '@override$eol$indent');
@@ -911,7 +911,7 @@
   Future<void> _addFix_addRequiredAnnotation() async {
     // TODO(brianwilkerson) Determine whether this await is necessary.
     await null;
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       builder.addSimpleInsertion(node.parent.offset, '@required ');
     });
@@ -923,7 +923,7 @@
     await null;
     FieldDeclaration declaration =
         node.thisOrAncestorOfType<FieldDeclaration>();
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       builder.addSimpleInsertion(declaration.offset, 'static ');
     });
@@ -933,7 +933,7 @@
   Future<void> _addFix_boolInsteadOfBoolean() async {
     // TODO(brianwilkerson) Determine whether this await is necessary.
     await null;
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       builder.addSimpleReplacement(range.error(error), 'bool');
     });
@@ -945,7 +945,7 @@
     await null;
     AstNode node = coveredNode;
     if (node is Expression) {
-      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+      var changeBuilder = _newDartChangeBuilder();
       await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
         AstNode parent = node.parent;
         while (parent != null) {
@@ -971,7 +971,7 @@
     String correction = lexeme.toLowerCase().contains('x')
         ? '0x${precise.toRadixString(16).toUpperCase()}'
         : precise.toString();
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       builder.addSimpleReplacement(range.node(integer), correction);
     });
@@ -994,7 +994,7 @@
           Expression initializer = coveredNode;
           DartType newType = initializer.staticType;
           if (newType is InterfaceType || newType is FunctionType) {
-            DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+            var changeBuilder = _newDartChangeBuilder();
             await changeBuilder.addFileEdit(file,
                 (DartFileEditBuilder builder) {
               builder.addReplacement(range.node(typeNode),
@@ -1024,7 +1024,7 @@
     // child: widget
     Expression expression = named.expression;
     if (flutter.isWidgetExpression(expression)) {
-      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+      var changeBuilder = _newDartChangeBuilder();
       await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
         flutter.convertChildToChildren2(
             builder,
@@ -1044,7 +1044,7 @@
     // child: [widget1, widget2]
     if (expression is ListLiteral &&
         expression.elements.every(flutter.isWidgetExpression)) {
-      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+      var changeBuilder = _newDartChangeBuilder();
       await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
         builder.addSimpleReplacement(range.node(named.name), 'children:');
         if (expression.typeArguments == null) {
@@ -1072,7 +1072,7 @@
           String indentNew = utils.getLinePrefix(named.offset);
           widgetText = _replaceSourceIndent(widgetText, indentOld, indentNew);
 
-          var builder = new DartChangeBuilder(session);
+          var builder = _newDartChangeBuilder();
           await builder.addFileEdit(file, (builder) {
             builder.addReplacement(range.node(named), (builder) {
               builder.write('child: ');
@@ -1144,7 +1144,7 @@
         return;
       }
 
-      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+      var changeBuilder = _newDartChangeBuilder();
       await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
         for (var argument in argumentToParameter.keys) {
           var parameter = argumentToParameter[argument];
@@ -1223,7 +1223,7 @@
     if (offset < 0) {
       return;
     }
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(filePath, (DartFileEditBuilder builder) {
       builder.addInsertion(offset, (DartEditBuilder builder) {
         builder.write(prefix);
@@ -1272,7 +1272,7 @@
     ClassMemberLocation targetLocation =
         utils.prepareNewConstructorLocation(classDeclaration);
 
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     if (flutter.isExactlyStatelessWidgetType(superType) ||
         flutter.isExactlyStatefulWidgetType(superType)) {
       // Specialize for Flutter widgets.
@@ -1351,7 +1351,7 @@
         utils.prepareNewConstructorLocation(targetNode);
     Source targetSource = targetElement.source;
     String targetFile = targetSource.fullName;
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(targetFile, (DartFileEditBuilder builder) {
       builder.addInsertion(targetLocation.offset, (DartEditBuilder builder) {
         builder.write(targetLocation.prefix);
@@ -1406,7 +1406,7 @@
     ClassMemberLocation targetLocation =
         utils.prepareNewConstructorLocation(targetNode);
     String targetFile = targetElement.source.fullName;
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       builder.addInsertion(targetLocation.offset, (DartEditBuilder builder) {
         builder.write(targetLocation.prefix);
@@ -1458,7 +1458,7 @@
         prefix = ', ';
       }
       String proposalName = _getConstructorProposalName(superConstructor);
-      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+      var changeBuilder = _newDartChangeBuilder();
       await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
         builder.addInsertion(insertOffset, (DartEditBuilder builder) {
           builder.write(prefix);
@@ -1519,7 +1519,7 @@
       ClassMemberLocation targetLocation =
           utils.prepareNewConstructorLocation(targetClassNode);
       String proposalName = _getConstructorProposalName(superConstructor);
-      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+      var changeBuilder = _newDartChangeBuilder();
       await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
         builder.addInsertion(targetLocation.offset, (DartEditBuilder builder) {
           void writeParameters(bool includeType) {
@@ -1627,7 +1627,7 @@
     // build field source
     Source targetSource = targetClassElement.source;
     String targetFile = targetSource.fullName;
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(targetFile, (DartFileEditBuilder builder) {
       Expression fieldTypeNode = climbPropertyAccess(nameNode);
       DartType fieldType = _inferUndefinedExpressionType(fieldTypeNode);
@@ -1667,7 +1667,7 @@
     //
     // Add proposal.
     //
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       DartType fieldType = parameter.type?.type;
       builder.addInsertion(targetLocation.offset, (DartEditBuilder builder) {
@@ -1792,7 +1792,7 @@
     // build method source
     Source targetSource = targetClassElement.source;
     String targetFile = targetSource.fullName;
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(targetFile, (DartFileEditBuilder builder) {
       builder.addInsertion(targetLocation.offset, (DartEditBuilder builder) {
         Expression fieldTypeNode = climbPropertyAccess(nameNode);
@@ -1820,7 +1820,7 @@
       if (source != null) {
         String file = source.fullName;
         if (isAbsolute(file) && AnalysisEngine.isDartFileName(file)) {
-          DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+          var changeBuilder = _newDartChangeBuilder();
           await changeBuilder.addFileEdit(source.fullName, (builder) {
             builder.addSimpleInsertion(0, '// TODO Implement this library.');
           });
@@ -1848,7 +1848,7 @@
       if (assignment.leftHandSide == node &&
           assignment.operator.type == TokenType.EQ &&
           assignment.parent is ExpressionStatement) {
-        DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+        var changeBuilder = _newDartChangeBuilder();
         await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
           builder.addSimpleInsertion(node.offset, 'var ');
         });
@@ -1873,7 +1873,7 @@
       return;
     }
     // build variable declaration source
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       builder.addInsertion(target.offset, (DartEditBuilder builder) {
         builder.writeLocalVariableDeclaration(name,
@@ -1915,7 +1915,7 @@
         utils.prepareNewClassMemberLocation(targetClass, (_) => true);
 
     String prefix = utils.getIndent(1);
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       builder.addInsertion(location.offset, (DartEditBuilder builder) {
         // Separator management.
@@ -2043,7 +2043,7 @@
     if (offset < 0) {
       return;
     }
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(filePath, (DartFileEditBuilder builder) {
       builder.addInsertion(offset, (DartEditBuilder builder) {
         builder.write(prefix);
@@ -2067,7 +2067,7 @@
     // prepare environment
     String prefix = utils.getIndent(1);
     int insertOffset = targetClass.end - 1;
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       builder.addInsertion(insertOffset, (DartEditBuilder builder) {
         builder.selectHere();
@@ -2094,7 +2094,7 @@
       Source source = partDirective.uriSource;
       if (source != null) {
         String libName = unitLibraryElement.name;
-        DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+        var changeBuilder = _newDartChangeBuilder();
         await changeBuilder.addFileEdit(source.fullName,
             (DartFileEditBuilder builder) {
           // TODO(brianwilkerson) Consider using the URI rather than name
@@ -2114,7 +2114,7 @@
       int startIndex = message.indexOf("'", message.indexOf("'") + 1) + 1;
       int endIndex = message.indexOf("'", startIndex);
       String typeName = message.substring(startIndex, endIndex);
-      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+      var changeBuilder = _newDartChangeBuilder();
       await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
         builder.addSimpleInsertion(
             declaration.typeParameters?.end ?? declaration.name.end,
@@ -2131,7 +2131,7 @@
     // prepare the existing type
     TypeAnnotation typeName = node.thisOrAncestorOfType<TypeAnnotation>();
     TypeProvider typeProvider = this.typeProvider;
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       builder.replaceTypeWithFuture(typeName, typeProvider);
     });
@@ -2147,7 +2147,7 @@
     // TODO(brianwilkerson) Determine whether this await is necessary.
     await null;
     String uriText;
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       uriText = builder.importLibrary(library);
     });
@@ -2181,7 +2181,7 @@
       // may be apply prefix
       PrefixElement prefix = imp.prefix;
       if (prefix != null) {
-        DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+        var changeBuilder = _newDartChangeBuilder();
         await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
           builder.addSimpleReplacement(
               range.startLength(node, 0), '${prefix.displayName}.');
@@ -2213,7 +2213,7 @@
         int length = showCombinator.end - offset;
         String libraryFile =
             context.resolveResult.libraryElement.source.fullName;
-        DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+        var changeBuilder = _newDartChangeBuilder();
         await changeBuilder.addFileEdit(libraryFile,
             (DartFileEditBuilder builder) {
           builder.addSimpleReplacement(
@@ -2308,7 +2308,7 @@
         return;
       }
       int insertOffset = error.offset + error.length;
-      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+      var changeBuilder = _newDartChangeBuilder();
       await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
         builder.addSimpleInsertion(insertOffset, ';');
       });
@@ -2336,7 +2336,7 @@
     } else {
       return;
     }
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       builder.addDeletion(range.token(negation));
       builder.addSimpleReplacement(range.node(identifier), 'isNotEmpty');
@@ -2349,7 +2349,7 @@
     await null;
     if (coveredNode is IsExpression) {
       IsExpression isExpression = coveredNode as IsExpression;
-      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+      var changeBuilder = _newDartChangeBuilder();
       await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
         builder
             .addReplacement(range.endEnd(isExpression.expression, isExpression),
@@ -2366,7 +2366,7 @@
     await null;
     if (coveredNode is IsExpression) {
       IsExpression isExpression = coveredNode as IsExpression;
-      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+      var changeBuilder = _newDartChangeBuilder();
       await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
         builder
             .addReplacement(range.endEnd(isExpression.expression, isExpression),
@@ -2387,7 +2387,7 @@
       return;
     }
     String className = enclosingClass.name.name;
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       builder.addSimpleInsertion(
           enclosingClass.classKeyword.offset, 'abstract ');
@@ -2418,7 +2418,7 @@
           Token keywordToken = declarationList.keyword;
           if (declarationList.variables.length == 1 &&
               keywordToken.keyword == Keyword.FINAL) {
-            DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+            var changeBuilder = _newDartChangeBuilder();
             await changeBuilder.addFileEdit(file,
                 (DartFileEditBuilder builder) {
               if (declarationList.type != null) {
@@ -2449,7 +2449,7 @@
       VariableDeclaration declaration = node.parent;
       VariableDeclarationList list = declaration.parent;
       if (list.variables.length == 1) {
-        DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+        var changeBuilder = _newDartChangeBuilder();
         await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
           if (list.keyword == null) {
             builder.addSimpleInsertion(list.offset, 'final ');
@@ -2477,7 +2477,7 @@
       if (element is ClassElement &&
           element.typeParameters != null &&
           element.typeParameters.length == typeArguments.arguments.length) {
-        DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+        var changeBuilder = _newDartChangeBuilder();
         await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
           String argumentText = utils.getNodeText(typeArguments);
           builder.addSimpleInsertion(typeName.end, argumentText);
@@ -2492,7 +2492,7 @@
   Future<void> _addFix_nonBoolCondition_addNotNull() async {
     // TODO(brianwilkerson) Determine whether this await is necessary.
     await null;
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       builder.addSimpleInsertion(error.offset + error.length, ' != null');
     });
@@ -2505,7 +2505,7 @@
     final awaitExpression = node;
     if (awaitExpression is AwaitExpression) {
       final awaitToken = awaitExpression.awaitKeyword;
-      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+      var changeBuilder = _newDartChangeBuilder();
       await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
         builder.addDeletion(range.startStart(awaitToken, awaitToken.next));
       });
@@ -2521,7 +2521,7 @@
       AstNode parent = coveredNode.parent;
       if (parent is BinaryExpression) {
         if (parent.rightOperand == coveredNode) {
-          DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+          var changeBuilder = _newDartChangeBuilder();
           await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
             builder.addDeletion(range.endEnd(parent.leftOperand, coveredNode));
           });
@@ -2540,7 +2540,7 @@
       if (statementsToRemove.isNotEmpty) {
         SourceRange rangeToRemove =
             utils.getLinesRangeStatements(statementsToRemove);
-        DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+        var changeBuilder = _newDartChangeBuilder();
         await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
           builder.addDeletion(rangeToRemove);
         });
@@ -2549,7 +2549,7 @@
     } else if (coveringNode is Statement) {
       SourceRange rangeToRemove =
           utils.getLinesRangeStatements(<Statement>[coveringNode]);
-      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+      var changeBuilder = _newDartChangeBuilder();
       await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
         builder.addDeletion(rangeToRemove);
       });
@@ -2560,7 +2560,7 @@
   Future<void> _addFix_removeEmptyCatch() async {
     // TODO(brianwilkerson) Determine whether this await is necessary.
     await null;
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       builder.addDeletion(utils.getLinesRange(range.node(node.parent)));
     });
@@ -2570,7 +2570,7 @@
   Future<void> _addFix_removeEmptyConstructorBody() async {
     // TODO(brianwilkerson) Determine whether this await is necessary.
     await null;
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       builder.addSimpleReplacement(
           utils.getLinesRange(range.node(node.parent)), ';');
@@ -2583,7 +2583,7 @@
     // TODO(brianwilkerson) Determine whether this await is necessary.
     await null;
     IfStatement ifStatement = node.parent;
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       builder.addDeletion(utils.getLinesRange(
           range.startEnd(ifStatement.elseKeyword, ifStatement.elseStatement)));
@@ -2596,13 +2596,13 @@
     await null;
     EmptyStatement emptyStatement = node;
     if (emptyStatement.parent is Block) {
-      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+      var changeBuilder = _newDartChangeBuilder();
       await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
         builder.addDeletion(utils.getLinesRange(range.node(emptyStatement)));
       });
       _addFixFromBuilder(changeBuilder, DartFixKind.REMOVE_EMPTY_STATEMENT);
     } else {
-      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+      var changeBuilder = _newDartChangeBuilder();
       await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
         Token previous = emptyStatement.findPrevious(emptyStatement.beginToken);
         if (previous != null) {
@@ -2623,7 +2623,7 @@
     if (ancestor == null) {
       return;
     }
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       builder.addDeletion(range.endEnd(ancestor.name, ancestor.initializer));
     });
@@ -2637,7 +2637,7 @@
     if (node is InterpolationExpression) {
       Token right = node.rightBracket;
       if (node.expression != null && right != null) {
-        DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+        var changeBuilder = _newDartChangeBuilder();
         await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
           builder.addSimpleReplacement(
               range.startStart(node, node.expression), r'$');
@@ -2655,7 +2655,7 @@
     MethodDeclaration declaration =
         node.thisOrAncestorOfType<MethodDeclaration>();
     if (declaration != null) {
-      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+      var changeBuilder = _newDartChangeBuilder();
       await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
         builder.addDeletion(utils.getLinesRange(range.node(declaration)));
       });
@@ -2672,7 +2672,7 @@
       SimpleIdentifier name = method.name;
       FunctionBody body = method.body;
       if (name != null && body != null) {
-        DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+        var changeBuilder = _newDartChangeBuilder();
         await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
           builder.addSimpleReplacement(range.endStart(name, body), ' ');
         });
@@ -2681,7 +2681,7 @@
       }
     } else if (node is FormalParameterList) {
       // Support for the fasta error.
-      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+      var changeBuilder = _newDartChangeBuilder();
       await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
         builder.addDeletion(range.node(node));
       });
@@ -2696,7 +2696,7 @@
     if (node is SimpleIdentifier && node.parent is MethodInvocation) {
       MethodInvocation invocation = node.parent as MethodInvocation;
       if (invocation.methodName == node && invocation.target != null) {
-        DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+        var changeBuilder = _newDartChangeBuilder();
         await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
           builder.addDeletion(range.endEnd(node, invocation));
         });
@@ -2714,13 +2714,13 @@
         : node.thisOrAncestorOfType<ThisExpression>();
     final parent = thisExpression?.parent;
     if (parent is PropertyAccess) {
-      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+      var changeBuilder = _newDartChangeBuilder();
       await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
         builder.addDeletion(range.startEnd(parent, parent.operator));
       });
       _addFixFromBuilder(changeBuilder, DartFixKind.REMOVE_THIS_EXPRESSION);
     } else if (parent is MethodInvocation) {
-      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+      var changeBuilder = _newDartChangeBuilder();
       await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
         builder.addDeletion(range.startEnd(parent, parent.operator));
       });
@@ -2733,7 +2733,7 @@
     await null;
     final TypeAnnotation type = node.thisOrAncestorOfType<TypeAnnotation>();
     if (type != null) {
-      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+      var changeBuilder = _newDartChangeBuilder();
       await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
         builder.addDeletion(range.startStart(type, type.endToken.next));
       });
@@ -2744,7 +2744,7 @@
   Future<void> _addFix_removeTypeArguments() async {
     if (coveredNode is TypeArgumentList) {
       TypeArgumentList typeArguments = coveredNode;
-      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+      var changeBuilder = _newDartChangeBuilder();
       await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
         builder.addDeletion(range.node(typeArguments));
       });
@@ -2762,7 +2762,7 @@
     Expression expression = asExpression.expression;
     int expressionPrecedence = getExpressionPrecedence(expression);
     // remove 'as T' from 'e as T'
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       builder.addDeletion(range.endEnd(expression, asExpression));
       _removeEnclosingParentheses(builder, asExpression, expressionPrecedence);
@@ -2777,7 +2777,7 @@
       AstNode catchClause = node.parent;
       if (catchClause is CatchClause &&
           catchClause.exceptionParameter == node) {
-        DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+        var changeBuilder = _newDartChangeBuilder();
         await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
           builder.addDeletion(
               range.startStart(catchClause.catchKeyword, catchClause.body));
@@ -2796,7 +2796,7 @@
       if (catchClause is CatchClause &&
           catchClause.stackTraceParameter == node &&
           catchClause.exceptionParameter != null) {
-        DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+        var changeBuilder = _newDartChangeBuilder();
         await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
           builder
               .addDeletion(range.endEnd(catchClause.exceptionParameter, node));
@@ -2817,7 +2817,7 @@
       return;
     }
     // remove the whole line with import
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       builder.addDeletion(utils.getLinesRange(range.node(importDirective)));
     });
@@ -2858,7 +2858,7 @@
     }
 
     // Compute the change.
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       for (var reference in references) {
         builder.addSimpleReplacement(range.node(reference), newName);
@@ -2872,7 +2872,7 @@
     // TODO(brianwilkerson) Determine whether this await is necessary.
     await null;
     if (node is VariableDeclarationList) {
-      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+      var changeBuilder = _newDartChangeBuilder();
       await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
         builder.addSimpleReplacement(
             range.token((node as VariableDeclarationList).keyword), 'const');
@@ -2884,7 +2884,7 @@
   Future<void> _addFix_replaceVarWithDynamic() async {
     // TODO(brianwilkerson) Determine whether this await is necessary.
     await null;
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       builder.addSimpleReplacement(range.error(error), 'dynamic');
     });
@@ -2911,7 +2911,7 @@
     if (thenStatement is ExpressionStatement) {
       final expression = thenStatement.expression.unParenthesized;
       if (expression is AssignmentExpression) {
-        DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+        var changeBuilder = _newDartChangeBuilder();
         await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
           builder.addReplacement(range.node(ifStatement),
               (DartEditBuilder builder) {
@@ -2932,7 +2932,7 @@
     await null;
     if (coveredNode is InstanceCreationExpression) {
       var instanceCreation = coveredNode as InstanceCreationExpression;
-      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+      var changeBuilder = _newDartChangeBuilder();
       await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
         if (instanceCreation.keyword == null) {
           builder.addSimpleInsertion(
@@ -2952,7 +2952,7 @@
     final FunctionTypedFormalParameter functionTyped =
         node.thisOrAncestorOfType<FunctionTypedFormalParameter>();
     if (functionTyped != null) {
-      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+      var changeBuilder = _newDartChangeBuilder();
       await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
         builder.addSimpleReplacement(range.node(functionTyped),
             utils.getNodeText(functionTyped.identifier));
@@ -2970,7 +2970,7 @@
         node.thisOrAncestorOfType<InstanceCreationExpression>();
     final InterfaceType type = instanceCreation.staticType;
     final generics = instanceCreation.constructorName.type.typeArguments;
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       builder.addReplacement(range.node(instanceCreation),
           (DartEditBuilder builder) {
@@ -2998,7 +2998,7 @@
     Future<void> addFixOfExpression(InvocationExpression expression) async {
       // TODO(brianwilkerson) Determine whether this await is necessary.
       await null;
-      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+      var changeBuilder = _newDartChangeBuilder();
       await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
         builder.addReplacement(range.node(ancestor), (DartEditBuilder builder) {
           if (expression is MethodInvocation && expression.target != null) {
@@ -3067,7 +3067,7 @@
       if (finder._element != null) {
         String closestName = finder._element.name;
         if (closestName != null) {
-          DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+          var changeBuilder = _newDartChangeBuilder();
           await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
             builder.addSimpleReplacement(range.node(node), closestName);
           });
@@ -3133,7 +3133,7 @@
       // if we have close enough element, suggest to use it
       if (finder._element != null) {
         String closestName = finder._element.name;
-        DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+        var changeBuilder = _newDartChangeBuilder();
         await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
           builder.addSimpleReplacement(range.node(node), closestName);
         });
@@ -3167,7 +3167,7 @@
     sourcePrefix = '$eol$eol';
     utils.targetClassElement = null;
     // build method source
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       builder.addInsertion(insertOffset, (DartEditBuilder builder) {
         builder.write(sourcePrefix);
@@ -3230,7 +3230,7 @@
       // If we have a close enough element, suggest to use it.
       if (finder._element != null) {
         String closestName = finder._element.name;
-        DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+        var changeBuilder = _newDartChangeBuilder();
         await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
           builder.addSimpleReplacement(range.node(node), closestName);
         });
@@ -3295,7 +3295,7 @@
           utils.prepareNewMethodLocation(targetClassNode);
       String targetFile = targetElement.source.fullName;
       // build method source
-      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+      var changeBuilder = _newDartChangeBuilder();
       await changeBuilder.addFileEdit(targetFile,
           (DartFileEditBuilder builder) {
         builder.addInsertion(targetLocation.offset, (DartEditBuilder builder) {
@@ -3369,7 +3369,7 @@
     if (flutter.isExactlyStatelessWidgetType(superType) ||
         flutter.isExactlyStatefulWidgetType(superType)) {
       if (parameters.isNotEmpty && parameters.last.isNamed) {
-        DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+        var changeBuilder = _newDartChangeBuilder();
         await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
           builder.addSimpleInsertion(
               parameters.last.end, ', $fieldParametersCode');
@@ -3388,7 +3388,7 @@
       }
     }
 
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
       // append new field formal initializers
       if (lastRequiredParameter != null) {
@@ -3444,7 +3444,7 @@
     if (newText == null) {
       return;
     }
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(pubspecFile.path,
         (DartFileEditBuilder builder) {
       builder.addSimpleReplacement(new SourceRange(offset, length), newText);
@@ -3460,7 +3460,7 @@
           n.offset == errorOffset &&
           n.length == errorLength) {
         Expression target = (n as MethodInvocation).target.unParenthesized;
-        DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+        var changeBuilder = _newDartChangeBuilder();
         await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
           // replace "/" with "~/"
           BinaryExpression binary = target as BinaryExpression;
@@ -3487,7 +3487,7 @@
     Element declaringElement = element.enclosingElement;
     if (declaringElement is ClassElement) {
       DartType declaringType = declaringElement.type;
-      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+      var changeBuilder = _newDartChangeBuilder();
       await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
         // replace "target" with class name
         builder.addReplacement(range.node(target), (DartEditBuilder builder) {
@@ -3552,7 +3552,7 @@
     // TODO(brianwilkerson) Determine whether this await is necessary.
     await null;
     // build method source
-    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    var changeBuilder = _newDartChangeBuilder();
     await changeBuilder.addFileEdit(targetFile, (DartFileEditBuilder builder) {
       builder.addInsertion(insertOffset, (DartEditBuilder builder) {
         builder.write(sourcePrefix);
@@ -3963,6 +3963,11 @@
     return false;
   }
 
+  DartChangeBuilder _newDartChangeBuilder() {
+    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
+    return changeBuilder;
+  }
+
   /**
    * Removes any [ParenthesizedExpression] enclosing [expr].
    *