Merge CommonElements and BackendHelpers!

pkg/compiler/lib/src/native/ssa.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.
 
 import '../common.dart';
 import '../constants/values.dart';
 import '../elements/resolution_types.dart';
 import '../elements/elements.dart';
 import '../js/js.dart' as js;
 import '../js_emitter/js_emitter.dart' show NativeEmitter;
@@ skipping 10 matching lines @@
 
   HInstruction convertDartClosure(
       ParameterElement parameter, ResolutionFunctionType type) {
     HInstruction local = builder.localsHandler.readLocal(parameter);
     ConstantValue arityConstant =
         builder.constantSystem.createInt(type.parameterTypes.length);
     HInstruction arity =
         builder.graph.addConstant(arityConstant, builder.closedWorld);
     // TODO(ngeoffray): For static methods, we could pass a method with a
     // defined arity.
-    MethodElement helper = builder.helpers.closureConverter;
+    MethodElement helper = builder.commonElements.closureConverter;
     builder.pushInvokeStatic(nativeBody, helper, [local, arity]);
     HInstruction closure = builder.pop();
     return closure;
   }
 
   // Check which pattern this native method follows:
   // 1) foo() native;
   //      hasBody = false
   // 2) foo() native "bar";
   //      No longer supported, this is now done with @JSName('foo') and case 1.
@@ skipping 72 matching lines @@
     LiteralString jsCode = nativeBody.asLiteralString();
     builder.push(new HForeignCode.statement(
         js.js.statementTemplateYielding(
             new js.LiteralStatement(jsCode.dartString.slowToString())),
         <HInstruction>[],
         new SideEffects(),
         null,
         builder.commonMasks.dynamicType));
   }
 }