Merge CommonElements and BackendHelpers!

pkg/compiler/lib/src/js_emitter/full_emitter/nsm_emitter.dart

 // Copyright (c) 2013, 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_emitter.full_emitter.nsm_emitter;
 
 import '../../elements/entities.dart';
 import '../../js/js.dart' as jsAst;
 import '../../js/js.dart' show js;
 import '../../js_backend/js_backend.dart' show GetterName, SetterName;
@@ skipping 158 matching lines @@
 
       if (!minify) {
         sortedLongs =
             sorted.map((selector) => selector.invocationMirrorMemberName);
       }
     }
     // Startup code that loops over the method names and puts handlers on the
     // Object class to catch noSuchMethod invocations.
     ClassEntity objectClass = compiler.commonElements.objectClass;
     jsAst.Expression createInvocationMirror = backend.emitter
-        .staticFunctionAccess(backend.helpers.createInvocationMirror);
+        .staticFunctionAccess(compiler.commonElements.createInvocationMirror);
     if (useDiffEncoding) {
       statements.add(js.statement(
           '''{
           var objectClassObject = processedClasses.collected[#objectClass],
               nameSequences = #diffEncoding.split("."),
               shortNames = [];
           if (objectClassObject instanceof Array)
               objectClassObject = objectClassObject[1];
           for (var j = 0; j < nameSequences.length; ++j) {
               var sequence = nameSequences[j].split(","),
@@ skipping 213 matching lines @@
   }
 
   String get value {
     if (_cachedValue == null) {
       _cachedValue = _computeDiffEncoding();
     }
 
     return _cachedValue;
   }
 }