Add type inference for assignments to properties.

pkg/front_end/lib/src/fasta/type_inference/type_inference_listener.dart

Index: pkg/front_end/lib/src/fasta/type_inference/type_inference_listener.dart
diff --git a/pkg/front_end/lib/src/fasta/type_inference/type_inference_listener.dart b/pkg/front_end/lib/src/fasta/type_inference/type_inference_listener.dart
index f250a951627bee114d4e977f461188922e141159..62a25442bd54c9f11cf8a5609a8d9f289c391fbc 100644
--- a/pkg/front_end/lib/src/fasta/type_inference/type_inference_listener.dart
+++ b/pkg/front_end/lib/src/fasta/type_inference/type_inference_listener.dart
@@ -206,6 +206,12 @@ class TypeInferenceListener
   void nullLiteralExit(NullLiteral expression, DartType inferredType) =>
       debugExpressionExit("nullLiteral", expression, inferredType);
 
+  bool propertyAssignEnter(Expression expression, DartType typeContext) =>
+      debugExpressionEnter("propertyAssign", expression, typeContext);
+
+  void propertyAssignExit(Expression expression, DartType inferredType) =>
+      debugExpressionExit("propertyAssign", expression, inferredType);
+
   bool propertyGetEnter(PropertyGet expression, DartType typeContext) =>
       debugExpressionEnter("propertyGet", expression, typeContext);