Replace Backend with JavaScriptBackend.

pkg/compiler/lib/src/js_backend/backend_helpers.dart

 // Copyright (c) 2015, 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 dart2js.js_backend.helpers;
 
 import '../common.dart';
 import '../common/names.dart' show Identifiers, Uris;
 import '../compiler.dart' show Compiler;
 import '../core_types.dart' show CommonElements, ElementEnvironment;
@@ skipping 86 matching lines @@
     assert(loadedLibraries.containsLibrary(DART_JS_HELPER));
 
     // TODO(johnniwinther): Avoid these. Currently needed to ensure resolution
     // of the classes for various queries in native behavior computation,
     // inference and codegen.
     _env.getThisType(jsArrayClass);
     _env.getThisType(jsExtendableArrayClass);
   }
 
   LibraryEntity _jsHelperLibrary;
-  LibraryEntity get jsHelperLibrary => _jsHelperLibrary ??= _env.lookupLibrary(DART_JS_HELPER);
+  LibraryEntity get jsHelperLibrary =>
+      _jsHelperLibrary ??= _env.lookupLibrary(DART_JS_HELPER);
 
   LibraryEntity _asyncLibrary;
-  LibraryEntity get asyncLibrary => _asyncLibrary ??= _env.lookupLibrary(Uris.dart_async);
+  LibraryEntity get asyncLibrary =>
+      _asyncLibrary ??= _env.lookupLibrary(Uris.dart_async);
 
   LibraryEntity _interceptorsLibrary;
-  LibraryEntity get interceptorsLibrary => _interceptorsLibrary ??= _env.lookupLibrary(DART_INTERCEPTORS);
+  LibraryEntity get interceptorsLibrary =>
+      _interceptorsLibrary ??= _env.lookupLibrary(DART_INTERCEPTORS);
 
   LibraryEntity _foreignLibrary;
-  LibraryEntity get foreignLibrary => _foreignLibrary ??= _env.lookupLibrary(DART_FOREIGN_HELPER);
+  LibraryEntity get foreignLibrary =>
+      _foreignLibrary ??= _env.lookupLibrary(DART_FOREIGN_HELPER);
 
   LibraryEntity _isolateHelperLibrary;
-  LibraryEntity get isolateHelperLibrary => _isolateHelperLibrary ??= _env.lookupLibrary(DART_ISOLATE_HELPER);
+  LibraryEntity get isolateHelperLibrary =>
+      _isolateHelperLibrary ??= _env.lookupLibrary(DART_ISOLATE_HELPER);
 
   /// Reference to the internal library to lookup functions to always inline.
   LibraryEntity _internalLibrary;
-  LibraryEntity get internalLibrary => _internalLibrary ??= _env.lookupLibrary(Uris.dart__internal);
+  LibraryEntity get internalLibrary =>
+      _internalLibrary ??= _env.lookupLibrary(Uris.dart__internal);
 
   FunctionEntity _assertTest;
   FunctionEntity get assertTest =>
       _assertTest ??= _findHelperFunction('assertTest');
 
   FunctionEntity _assertThrow;
   FunctionEntity get assertThrow =>
       _assertThrow ??= _findHelperFunction('assertThrow');
 
   FunctionEntity _assertHelper;
@@ skipping 640 matching lines @@
   ClassEntity get annotationReturnsClass => _findHelperClass('Returns');
 
   ClassEntity get annotationJSNameClass => _findHelperClass('JSName');
 
   FunctionEntity get toStringForNativeObject =>
       _findHelperFunction('toStringForNativeObject');
 
   FunctionEntity get hashCodeForNativeObject =>
       _findHelperFunction('hashCodeForNativeObject');
 }