Annotate targets of implicit this property gets/sets in inference tests.

pkg/front_end/testcases/inference/infer_type_on_var_from_field.dart

 // Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /*@testedFeatures=inference*/
 library test;
 
 class A {
   int x = 0;
 
   test1() {
-    var /*@type=int*/ a = x;
+    var /*@type=int*/ a = /*@target=A::x*/ x;
     a = /*error:INVALID_ASSIGNMENT*/ "hi";
     a = 3;
-    var /*@type=int*/ b = y;
+    var /*@type=int*/ b = /*@target=A::y*/ y;
     b = /*error:INVALID_ASSIGNMENT*/ "hi";
     b = 4;
-    var /*@type=int*/ c = z;
+    var /*@type=int*/ c = /*@target=A::z*/ z;
     c = /*error:INVALID_ASSIGNMENT*/ "hi";
     c = 4;
   }
 
   int y; // field def after use
   final /*@topType=int*/ z = 42; // should infer `int`
 }