Big merge from experimental to bleeding edge.

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 'dart:uri';
 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';
@@ skipping 441 matching lines @@
 }
 ''';
   MockCompiler compiler = new MockCompiler();
   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;
   LocalPlaceholder fooPlaceholder =
-      collector.functionScopes[mainElement].localPlaceholders.iterator().next();
+      collector.functionScopes[mainElement].localPlaceholders.first;
   Expect.isTrue(fooPlaceholder.nodes.contains(fooNode.name));
 }
 
 testDefaultClassNamePlaceholder() {
   var src = '''
 interface I default C{
   I();
 }
 
 class C {
@@ skipping 278 matching lines @@
   testStaticAccessIoLib();
   testLocalFunctionPlaceholder();
   testMinification();
   testClosureLocalsMinified();
   testParametersMinified();
   testDeclarationTypePlaceholders();
   testPlatformLibraryMemberNamesAreFixed();
   testConflictsWithCoreLib();
   testUnresolvedNamedConstructor();
 }