Add type inference for `this` expressions.

pkg/front_end/lib/src/fasta/kernel/kernel_field_builder.dart

Index: pkg/front_end/lib/src/fasta/kernel/kernel_field_builder.dart
diff --git a/pkg/front_end/lib/src/fasta/kernel/kernel_field_builder.dart b/pkg/front_end/lib/src/fasta/kernel/kernel_field_builder.dart
index d7c9b7d06ff0a5439913ca3449fa149ee50880a8..3b863d59bc152ca2019ff1da35f02401afb35f8c 100644
--- a/pkg/front_end/lib/src/fasta/kernel/kernel_field_builder.dart
+++ b/pkg/front_end/lib/src/fasta/kernel/kernel_field_builder.dart
@@ -73,8 +73,8 @@ class KernelFieldBuilder extends FieldBuilder<Expression> {
       // should it be the part URI?
       var typeInferenceEngine = library.loader.typeInferenceEngine;
       var listener = new TypeInferenceListener();
-      var typeInferrer =
-          typeInferenceEngine.createTopLevelTypeInferrer(field, listener);
+      var typeInferrer = typeInferenceEngine.createTopLevelTypeInferrer(
+          field, listener, field.enclosingClass?.thisType);

[scheglov, 2017/06/05 17:40:02]

Nit: The order is not logical - it would be better to have listener, then the
enclosing type, then the field.

[Paul Berry, 2017/06/05 18:37:16]

Thanks.  Fixed.

       var bodyBuilder = new BodyBuilder(
           library,
           this,