Refactor BackendHelpers to be reusageable with KernelWorldBuilder

pkg/compiler/lib/src/js_emitter/interceptor_stub_generator.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.interceptor_stub_generator;
 
 import '../compiler.dart' show Compiler;
 import '../constants/values.dart';
 import '../elements/entities.dart';
 import '../elements/types.dart' show InterfaceType;
@@ skipping 250 matching lines @@
       //    if (typeof a0 === "number") {
       //      if (receiver.constructor == Array && !receiver.immutable$list) {
       //        if (a0 >>> 0 === a0 && a0 < receiver.length) {
       //          return receiver[a0] = a1;
       //        }
       //      }
       //    }
       bool containsArray = classes.contains(helpers.jsArrayClass);
       bool containsString = classes.contains(helpers.jsStringClass);
       bool containsJsIndexable =
-          helpers.jsIndexingBehaviorInterface.isResolved &&
+          closedWorld.isImplemented(helpers.jsIndexingBehaviorInterface) &&
               classes.any((cls) {
                 return closedWorld.isSubtypeOf(
                     cls, helpers.jsIndexingBehaviorInterface);
               });
       // The index set operator requires a check on its set value in
       // checked mode, so we don't optimize the interceptor if the
       // compiler has type assertions enabled.
       if (selector.isIndexSet &&
           (compiler.options.enableTypeAssertions || !containsArray)) {
         return null;
@@ skipping 64 matching lines @@
 
     if (selector.isSetter) {
       parameterNames.add('value');
     } else {
       for (int i = 0; i < selector.argumentCount; i++) {
         parameterNames.add('a$i');
       }
     }
 
     jsAst.Name invocationName = backend.namer.invocationName(selector);
-    String globalObject = namer.globalObjectFor(helpers.interceptorsLibrary);
+    String globalObject =
+        namer.globalObjectForLibrary(helpers.interceptorsLibrary);
 
     jsAst.Statement optimizedPath =
         _fastPathForOneShotInterceptor(selector, classes);
     if (optimizedPath == null) optimizedPath = js.statement(';');
 
     return js('function(#) { #; return #.#(receiver).#(#) }', [
       parameterNames,
       optimizedPath,
       globalObject,
       getInterceptorName,
@@ skipping 43 matching lines @@
         }
 
         var map = new jsAst.ObjectInitializer(properties);
         elements.add(map);
       }
     }
 
     return new jsAst.ArrayInitializer(elements);
   }
 }