Replace Backend with JavaScriptBackend.

pkg/compiler/lib/src/deferred_load.dart

 // Copyright (c) 2014, 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 deferred_load;
 
-import 'common/backend_api.dart' show Backend;
 import 'common/tasks.dart' show CompilerTask;
 import 'common.dart';
 import 'compiler.dart' show Compiler;
 import 'constants/expressions.dart' show ConstantExpression;
 import 'constants/values.dart'
     show
         ConstantValue,
         ConstructedConstantValue,
         DeferredConstantValue,
         StringConstantValue;
@@ skipping 132 matching lines @@
 
   Set<Element> _mainElements = new Set<Element>();
 
   final Compiler compiler;
   DeferredLoadTask(Compiler compiler)
       : compiler = compiler,
         super(compiler.measurer) {
     mainOutputUnit.imports.add(_fakeMainImport);
   }
 
-  Backend get backend => compiler.backend;
+  JavaScriptBackend get backend => compiler.backend;
   DiagnosticReporter get reporter => compiler.reporter;
 
   /// Returns the [OutputUnit] where [element] belongs.
   OutputUnit outputUnitForElement(Element element) {
     if (!isProgramSplit) return mainOutputUnit;
 
     element = element.implementation;
     while (!_elementToOutputUnit.containsKey(element)) {
       // TODO(21051): workaround: it looks like we output annotation constants
       // for classes that we don't include in the output. This seems to happen
@@ skipping 881 matching lines @@
 
   bool operator ==(other) {
     if (other is! _DeclaredDeferredImport) return false;
     return declaration == other.declaration;
   }
 
   int get hashCode => declaration.hashCode * 17;
 
   String toString() => '$declaration';
 }