Add FrontendStrategy.commonElements and remove Backend.commonElements

pkg/compiler/lib/src/js_emitter/full_emitter/emitter.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 dart2js.js_emitter.full_emitter;
 
 import 'dart:collection' show HashMap;
 import 'dart:convert';
 
 import 'package:js_runtime/shared/embedded_names.dart' as embeddedNames;
@@ skipping 791 matching lines @@
         generateEmbeddedGlobalAccess(embeddedNames.ALL_CLASSES);
     jsAst.Expression getTypeFromNameAccess =
         generateEmbeddedGlobalAccess(embeddedNames.GET_TYPE_FROM_NAME);
     jsAst.Expression interceptorsByTagAccess =
         generateEmbeddedGlobalAccess(embeddedNames.INTERCEPTORS_BY_TAG);
     jsAst.Expression leafTagsAccess =
         generateEmbeddedGlobalAccess(embeddedNames.LEAF_TAGS);
     jsAst.Expression finishedClassesAccess =
         generateEmbeddedGlobalAccess(embeddedNames.FINISHED_CLASSES);
     jsAst.Expression cyclicThrow =
-        staticFunctionAccess(backend.commonElements.cyclicThrowHelper);
+        staticFunctionAccess(compiler.commonElements.cyclicThrowHelper);
     jsAst.Expression laziesAccess =
         generateEmbeddedGlobalAccess(embeddedNames.LAZIES);
 
     return js.statement(
         '''
       function init() {
         $isolatePropertiesName = Object.create(null);
         #allClasses = map();
         #getTypeFromName = function(name) {return #allClasses[name];};
         #interceptorsByTag = map();
@@ skipping 1098 matching lines @@
     // data.
     mapping["_comment"] = "This mapping shows which compiled `.js` files are "
         "needed for a given deferred library import.";
     mapping.addAll(compiler.deferredLoadTask.computeDeferredMap());
     compiler.outputProvider(
         compiler.options.deferredMapUri.path, '', OutputType.info)
       ..add(const JsonEncoder.withIndent("  ").convert(mapping))
       ..close();
   }
 }