Refactor scope handling.

tests/compiler/dart2js/mock_compiler.dart

Index: tests/compiler/dart2js/mock_compiler.dart
diff --git a/tests/compiler/dart2js/mock_compiler.dart b/tests/compiler/dart2js/mock_compiler.dart
index e1379387f7cab1210f845aa121724f9ada3f9a4a..8694ef6b7ec80141f3c4964de7b108c03bd480fc 100644
--- a/tests/compiler/dart2js/mock_compiler.dart
+++ b/tests/compiler/dart2js/mock_compiler.dart
@@ -124,11 +124,11 @@ class MockCompiler extends Compiler {
 
   TreeElementMapping resolveNodeStatement(Node tree, Element element) {
     ResolverVisitor visitor = new ResolverVisitor(this, element);
-    if (visitor.context is TopScope) {
-      visitor.context = new BlockScope(visitor.context);
+    if (visitor.scope is TopScope) {
+      visitor.scope = new BlockScope(visitor.scope);
     }
     visitor.visit(tree);
-    visitor.context = new TopScope(element.getLibrary());
+    visitor.scope = new TopScope(element.getLibrary());
     // Resolve the type annotations encountered in the code.
     while (!resolver.toResolve.isEmpty()) {
       resolver.toResolve.removeFirst().ensureResolved(this);
@@ -140,7 +140,7 @@ class MockCompiler extends Compiler {
     Element mockElement =
         new Element(buildSourceString(''), ElementKind.FUNCTION, mainApp);
     ResolverVisitor visitor = new ResolverVisitor(this, mockElement);
-    visitor.context = new BlockScope(visitor.context);
+    visitor.scope = new BlockScope(visitor.scope);
     return visitor;
   }