Remove warnings from dart2js test-suite.

tests/compiler/dart2js/dart_backend_test.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.
 
 import "package:expect/expect.dart";
 import 'dart:async';
 import "package:async_helper/async_helper.dart";
-import 'parser_helper.dart';
 import 'mock_compiler.dart';
 import '../../../sdk/lib/_internal/compiler/compiler.dart';
 import '../../../sdk/lib/_internal/compiler/implementation/dart2jslib.dart' as leg;
 import '../../../sdk/lib/_internal/compiler/implementation/dart_backend/dart_backend.dart';
 import '../../../sdk/lib/_internal/compiler/implementation/elements/elements.dart';
 import '../../../sdk/lib/_internal/compiler/implementation/tree/tree.dart';
 
 const coreLib = r'''
 library corelib;
 class Object {
@@ skipping 425 matching lines @@
   testDart2Dart('main(){new A().field;}class B{}class A{B field;}');
 }
 
 class DynoMap implements Map<Element, ElementAst> {
   final compiler;
   DynoMap(this.compiler);
 
   get resolvedElements => compiler.enqueuer.resolution.resolvedElements;
   ElementAst operator[](Element element) =>
       new ElementAst(element.parseNode(compiler), resolvedElements[element]);
+
+  noSuchMethod(Invocation invocation) => throw 'unimplemented method';
 }
 
 PlaceholderCollector collectPlaceholders(compiler, element) =>
   new PlaceholderCollector(compiler, new Set<String>(), new DynoMap(compiler))
       ..collect(element);
 
 testLocalFunctionPlaceholder() {
   var src = '''
 main() {
   function localfoo() {}
   localfoo();
 }
 ''';
   MockCompiler compiler = new MockCompiler(emitJavaScript: false);
   assert(compiler.backend is DartBackend);
   compiler.parseScript(src);
   FunctionElement mainElement = compiler.mainApp.find(leg.Compiler.MAIN);
   compiler.processQueue(compiler.enqueuer.resolution, mainElement);
   PlaceholderCollector collector = collectPlaceholders(compiler, mainElement);
   FunctionExpression mainNode = mainElement.parseNode(compiler);
-  FunctionExpression fooNode = mainNode.body.statements.nodes.head.function;
+  Block body = mainNode.body;
+  FunctionDeclaration functionDeclaration = body.statements.nodes.head;
+  FunctionExpression fooNode = functionDeclaration.function;
   LocalPlaceholder fooPlaceholder =
       collector.functionScopes[mainElement].localPlaceholders.first;
   Expect.isTrue(fooPlaceholder.nodes.contains(fooNode.name));
 }
 
 testTypeVariablesAreRenamed() {
   // Somewhat a hack: we require all the references of the identifier
   // to be renamed in the same way for the whole library. Hence
   // if we have a class and type variable with the same name, they
   // both should be renamed.
@@ skipping 251 matching lines @@
   testStaticAccessIoLib();
   testLocalFunctionPlaceholder();
   testMinification();
   testClosureLocalsMinified();
   testParametersMinified();
   testDeclarationTypePlaceholders();
   testPlatformLibraryMemberNamesAreFixed();
   testConflictsWithCoreLib();
   testUnresolvedNamedConstructor();
 }