Only emit members in mirror helper symbolsmap.

tests/compiler/dart2js/mirror_helper_test.dart

 // Copyright (c) 2013, 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 "package:expect/expect.dart";
 import 'memory_compiler.dart' show compilerFor;
 import '../../../sdk/lib/_internal/compiler/implementation/apiimpl.dart' show
     Compiler;
 import
     '../../../sdk/lib/_internal/compiler/implementation/elements/elements.dart'
@@ skipping 40 matching lines @@
   Compiler compiler = runCompiler(useMirrorHelperLibrary: true, minify: minify);
 
   DartBackend backend = compiler.backend;
   MirrorRenamer mirrorRenamer = backend.mirrorRenamer;
   Map<Node, String> renames = backend.renames;
   Map<LibraryElement, String> imports = backend.imports;
 
   Node getNameFunctionNode =
       backend.memberNodes.values.first.first.body.statements.nodes.head;
 
-  Expect.equals(
-      const SourceString(MirrorRenamer.MIRROR_HELPER_GET_NAME_FUNCTION),
-      mirrorRenamer.symbols[renames[getNameFunctionNode.expression.selector]]);
+  Expect.equals(renames[mirrorRenamer.mirrorHelperGetNameFunctionNode.name],
+                renames[getNameFunctionNode.expression.selector]);
   Expect.equals("",
                 renames[getNameFunctionNode.expression.receiver]);
   Expect.equals(1, imports.keys.length);
 }
 
 void testWithoutMirrorRenaming({bool minify}) {
   Compiler compiler =
       runCompiler(useMirrorHelperLibrary: false, minify: minify);
 
   DartBackend backend = compiler.backend;
@@ skipping 15 matching lines @@
 class Foo {
   noSuchMethod(Invocation invocation) {
     MirrorSystem.getName(invocation.memberName);
   }
 }
 
 void main() {
   new Foo().fisk();
 }
 """};