Introduce "CommonElements"

pkg/compiler/lib/src/js_backend/backend_impact.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_helpers.impact;
 
 import '../compiler.dart' show Compiler;
-import '../core_types.dart' show CoreClasses;
+import '../core_types.dart' show CommonElements;
 import '../dart_types.dart' show InterfaceType;
 import '../elements/elements.dart' show ClassElement, Element;
 import 'backend_helpers.dart';
 import 'constant_system_javascript.dart';
 import 'js_backend.dart';
 
 /// A set of JavaScript backend dependencies.
 class BackendImpact {
   final List<Element> staticUses;
   final List<InterfaceType> instantiatedTypes;
@@ skipping 10 matching lines @@
 /// The JavaScript backend dependencies for various features.
 class BackendImpacts {
   final Compiler compiler;
 
   BackendImpacts(this.compiler);
 
   JavaScriptBackend get backend => compiler.backend;
 
   BackendHelpers get helpers => backend.helpers;
 
-  CoreClasses get coreClasses => compiler.coreClasses;
+  CommonElements get commonElements => compiler.commonElements;
 
   BackendImpact _getRuntimeTypeArgument;
 
   BackendImpact get getRuntimeTypeArgument {
     if (_getRuntimeTypeArgument == null) {
       _getRuntimeTypeArgument = new BackendImpact(staticUses: [
         helpers.getRuntimeTypeArgument,
         helpers.getTypeArgumentByIndex,
       ]);
     }
@@ skipping 243 matching lines @@
           new BackendImpact(staticUses: [helpers.symbolValidatedConstructor]);
     }
     return _symbolConstructor;
   }
 
   BackendImpact _constSymbol;
 
   BackendImpact get constSymbol {
     if (_constSymbol == null) {
       _constSymbol = new BackendImpact(
-          instantiatedClasses: [coreClasses.symbolClass],
-          staticUses: [compiler.symbolConstructor.declaration]);
+          instantiatedClasses: [commonElements.symbolClass],
+          staticUses: [commonElements.symbolConstructor.declaration]);
     }
     return _constSymbol;
   }
 
   BackendImpact _incDecOperation;
 
   BackendImpact get incDecOperation {
     if (_incDecOperation == null) {
       _incDecOperation =
           _needsInt('Needed for the `+ 1` or `- 1` operation of ++/--.');
@@ skipping 276 matching lines @@
         helpers.defineProperty
       ]);
     }
     return _nativeTypeCheck;
   }
 
   BackendImpact _closure;
 
   BackendImpact get closure {
     if (_closure == null) {
-      _closure =
-          new BackendImpact(instantiatedClasses: [coreClasses.functionClass]);
+      _closure = new BackendImpact(
+          instantiatedClasses: [commonElements.functionClass]);
     }
     return _closure;
   }
 }