Stop using deprecated ContextLocator and ContextBuilder. (#4326)

lib/src/dart.dart

diff --git a/lib/src/dart.dart b/lib/src/dart.dart
index 56e69f5f..1ed734f 100644
--- a/lib/src/dart.dart
+++ b/lib/src/dart.dart
@@ -8,8 +8,7 @@
 import 'dart:async';
 import 'dart:io';
 
-import 'package:analyzer/dart/analysis/context_builder.dart';
-import 'package:analyzer/dart/analysis/context_locator.dart';
+import 'package:analyzer/dart/analysis/analysis_context_collection.dart';
 import 'package:analyzer/dart/analysis/results.dart';
 import 'package:analyzer/dart/analysis/session.dart';
 import 'package:analyzer/dart/ast/ast.dart';
@@ -33,17 +32,9 @@
       );
 
   AnalysisContextManager._(this.packagePath)
-      : _session = ContextBuilder()
-            .createContext(
-              contextRoot: ContextLocator().locateRoots(
-                includedPaths: [p.absolute(p.normalize(packagePath))],
-                optionsFile:
-                    // We don't want to take 'analysis_options.yaml' files into
-                    // account. So we replace it with an empty file.
-                    Platform.isWindows ? r'C:\NUL' : '/dev/null',
-              ).first,
-            )
-            .currentSession;
+      : _session = AnalysisContextCollection(
+          includedPaths: [packagePath],
+        ).contextFor(packagePath).currentSession;
 
   /// Parse the file with the given [path] into AST.
   ///

pubspec.yaml

diff --git a/pubspec.yaml b/pubspec.yaml
index 9525507..4942604 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -4,7 +4,7 @@
   sdk: ^3.2.0
 
 dependencies:
-  analyzer: ^6.3.0
+  analyzer: ^6.8.0
   args: ^2.5.0
   async: ^2.11.0
   cli_util: ^0.4.1