Split getClosureRepresentationInfo into MemberEntity and (ir/ast) nodes

tests/compiler/dart2js/serialization/model_test_helper.dart

 // Copyright (c) 2015, 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.serialization_model_test;
 
 import 'dart:async';
 import 'package:async_helper/async_helper.dart';
 import 'package:expect/expect.dart';
 import 'package:compiler/src/closure.dart';
@@ skipping 148 matching lines @@
 
 void checkElements(
     Compiler compiler1, Compiler compiler2, Element element1, Element element2,
     {bool verbose: false}) {
   if (element1.isAbstract) return;
   if (element1.isFunction ||
       element1.isConstructor ||
       (element1.isField && element1.isInstanceMember)) {
     ClosureRepresentationInfo closureData1 = compiler1
         .backendStrategy.closureDataLookup
-        .getClosureRepresentationInfo(element1);
+        .getClosureInfoForMember(element1 as MemberElement);
     ClosureRepresentationInfo closureData2 = compiler2
         .backendStrategy.closureDataLookup
-        .getClosureRepresentationInfo(element2);
+        .getClosureInfoForMember(element2 as MemberElement);
 
     checkElementIdentities(
         closureData1,
         closureData2,
         '$element1.closureEntity',
         closureData1.closureEntity,
         closureData2.closureEntity);
     checkElementIdentities(
         closureData1,
         closureData2,
@@ skipping 110 matching lines @@
   check(outputUnit1, outputUnit2, 'OutputUnit.isMainOutput $message',
       outputUnit1.isMainOutput, outputUnit2.isMainOutput);
   checkSetEquivalence(
       outputUnit1,
       outputUnit2,
       'OutputUnit.imports $message',
       outputUnit1.imports,
       outputUnit2.imports,
       (a, b) => areElementsEquivalent(a.declaration, b.declaration));
 }