Make selector registration in the resolver and code generator more explicit.

tests/compiler/dart2js/mock_compiler.dart

 // Copyright (c) 2012, 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.
 
 #library('mock_compiler');
 
 #import("dart:uri");
 
 #import("../../../lib/compiler/implementation/elements/elements.dart");
 #import("../../../lib/compiler/implementation/leg.dart");
@@ skipping 117 matching lines @@
   }
 
   TreeElementMapping resolveStatement(String text) {
     parsedTree = parseStatement(text);
     return resolveNodeStatement(parsedTree, mainApp);
   }
 
   TreeElementMapping resolveNodeStatement(Node tree, Element element) {
     ResolverVisitor visitor = new ResolverVisitor(this, element);
     if (visitor.scope is TopScope) {
-      visitor.scope = new BlockScope(visitor.scope);
+      visitor.scope = new MethodScope(visitor.scope, element);
     }
     visitor.visit(tree);
     visitor.scope = new TopScope(element.getLibrary());
     return visitor.mapping;
   }
 
   resolverVisitor() {
     Element mockElement =
         new Element(buildSourceString(''), ElementKind.FUNCTION, mainApp);
     ResolverVisitor visitor = new ResolverVisitor(this, mockElement);
-    visitor.scope = new BlockScope(visitor.scope);
+    visitor.scope = new MethodScope(visitor.scope, mockElement);
     return visitor;
   }
 
   parseScript(String text, [LibraryElement library]) {
     if (library === null) library = mainApp;
     parseUnit(text, this, library);
   }
 
   void scanBuiltinLibraries() {
     // Do nothing. The mock core library is already handled in the constructor.
@@ skipping 42 matching lines @@
     });
   }
 }
 
 LibraryElement mockLibrary(Compiler compiler, String source) {
   Uri uri = new Uri.fromComponents(scheme: "source");
   var library = new LibraryElement(new Script(uri, new MockFile(source)));
   importLibrary(library, compiler.coreLibrary, compiler);
   return library;
 }