Use index in J/KTypeVariable and fix remaining inequivalence

pkg/compiler/lib/src/ssa/builder.dart

 // Copyright (c) 2012, 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.
 
 import 'dart:collection';
 
 import 'package:js_runtime/shared/embedded_names.dart';
 
 import '../closure.dart';
 import '../common.dart';
@@ skipping 709 matching lines @@
       closeAndGotoExit(new HReturn(
           value, sourceInformationBuilder.buildReturn(functionElement.node)));
       return closeFunction();
     }
     assert(!function.modifiers.isExternal, failedAt(functionElement));
 
     // If [functionElement] is `operator==` we explicitly add a null check at
     // the beginning of the method. This is to avoid having call sites do the
     // null check.
     if (name == '==') {
-      if (!backend.operatorEqHandlesNullArgument(functionElement)) {
+      if (!commonElements.operatorEqHandlesNullArgument(functionElement)) {
         handleIf(
             node: function,
             visitCondition: () {
               HParameterValue parameter = parameters.values.first;
               push(new HIdentity(parameter, graph.addConstantNull(closedWorld),
                   null, commonMasks.boolType));
             },
             visitThen: () {
               closeAndGotoExit(new HReturn(
                   graph.addConstantBool(false, closedWorld),
@@ skipping 6103 matching lines @@
       this.oldReturnLocal,
       this.oldReturnType,
       this.oldResolvedAst,
       this.oldStack,
       this.oldLocalsHandler,
       this.inTryStatement,
       this.allFunctionsCalledOnce,
       this.oldElementInferenceResults)
       : super(function);
 }