Observatory strong mode fixes: Change types of InstanceMock/Instance members.

The types now correspond in the two classes, so we avoid invalid
override errors.

Change-Id: Iceeb324e6adf7573ae39d7250184f7eb58656498
Reviewed-on: https://dart-review.googlesource.com/56021
Reviewed-by: Ryan Macnak <rmacnak@google.com>
Commit-Queue: Paul Berry <paulberry@google.com>
diff --git a/runtime/observatory/lib/src/models/objects/instance.dart b/runtime/observatory/lib/src/models/objects/instance.dart
index 982d6d8..1a1b8d4 100644
--- a/runtime/observatory/lib/src/models/objects/instance.dart
+++ b/runtime/observatory/lib/src/models/objects/instance.dart
@@ -420,37 +420,37 @@
   ///
   /// Provided for instance kinds:
   ///   RegExp
-  Function get oneByteFunction;
+  FunctionRef get oneByteFunction;
 
   /// [optional]
   ///
   /// Provided for instance kinds:
   ///   RegExp
-  Function get twoByteFunction;
+  FunctionRef get twoByteFunction;
 
   /// [optional]
   ///
   /// Provided for instance kinds:
   ///   RegExp
-  Function get externalOneByteFunction;
+  FunctionRef get externalOneByteFunction;
 
   /// [optional]
   ///
   /// Provided for instance kinds:
   ///   RegExp
-  Function get externalTwoByteFunction;
+  FunctionRef get externalTwoByteFunction;
 
   /// [optional]
   ///
   /// Provided for instance kinds:
   ///   RegExp
-  Instance get oneByteBytecode;
+  InstanceRef get oneByteBytecode;
 
   /// [optional]
   ///
   /// Provided for instance kinds:
   ///   RegExp
-  Instance get twoByteBytecode;
+  InstanceRef get twoByteBytecode;
 }
 
 abstract class BoundField {
diff --git a/runtime/observatory/tests/observatory_ui/mocks/objects/instance.dart b/runtime/observatory/tests/observatory_ui/mocks/objects/instance.dart
index aa72df2..df07d2c 100644
--- a/runtime/observatory/tests/observatory_ui/mocks/objects/instance.dart
+++ b/runtime/observatory/tests/observatory_ui/mocks/objects/instance.dart
@@ -50,7 +50,7 @@
   final M.ContextRef closureContext;
   final int offset;
   final int count;
-  final Iterable<dynamic> typedElements;
+  final List<dynamic> typedElements;
   final Iterable<M.BoundField> fields;
   final Iterable<M.NativeField> nativeFields;
   final Iterable<M.Guarded<M.ObjectRef>> elements;