Revert "Remove Compiler.assembledCode."

tests/compiler/dart2js/mirror_helper_rename_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 'dart:async';
 import "package:async_helper/async_helper.dart";
-import 'memory_compiler.dart' show compilerFor, OutputCollector;
+import 'memory_compiler.dart' show compilerFor;
 import 'package:compiler/src/apiimpl.dart' show
     Compiler;
 import 'package:compiler/src/tree/tree.dart' show
     Node;
 import 'package:compiler/src/dart_backend/dart_backend.dart';
 import 'package:compiler/src/mirror_renamer/mirror_renamer.dart';
 
 main() {
   testWithMirrorHelperLibrary(minify: true);
   testWithMirrorHelperLibrary(minify: false);
   testWithoutMirrorHelperLibrary(minify: true);
   testWithoutMirrorHelperLibrary(minify: false);
 }
 
-Future<Compiler> runCompiler({OutputCollector outputCollector,
-                              bool useMirrorHelperLibrary: false,
-                              bool minify: false}) {
+Future<Compiler> runCompiler({useMirrorHelperLibrary: false, minify: false}) {
   List<String> options = ['--output-type=dart'];
   if (minify) {
     options.add('--minify');
   }
-  Compiler compiler = compilerFor(
-      MEMORY_SOURCE_FILES, outputProvider: outputCollector, options: options);
+  Compiler compiler = compilerFor(MEMORY_SOURCE_FILES, options: options);
   DartBackend backend = compiler.backend;
   backend.useMirrorHelperLibrary = useMirrorHelperLibrary;
   return
       compiler.runCompiler(Uri.parse('memory:main.dart')).then((_) => compiler);
 }
 
 void testWithMirrorHelperLibrary({bool minify}) {
-  OutputCollector outputCollector = new OutputCollector();
-  asyncTest(() =>
-    runCompiler(outputCollector: outputCollector,
-                useMirrorHelperLibrary: true,
-                minify: minify)
-      .then((Compiler compiler) {
+  asyncTest(() => runCompiler(useMirrorHelperLibrary: true, minify: minify).
+      then((Compiler compiler) {
     DartBackend backend = compiler.backend;
     MirrorRenamerImpl mirrorRenamer = backend.mirrorRenamer;
     Map<Node, String> renames = backend.placeholderRenamer.renames;
     Map<String, String> symbols = mirrorRenamer.symbols;
 
     Expect.isFalse(null == mirrorRenamer.helperLibrary);
     Expect.isFalse(null == mirrorRenamer.getNameFunction);
 
     for (Node n in renames.keys) {
       if (symbols.containsKey(renames[n])) {
         if(n.toString() == 'getName') {
           Expect.equals(
               MirrorRenamerImpl.MIRROR_HELPER_GET_NAME_FUNCTION,
               symbols[renames[n]]);
         } else {
           Expect.equals(n.toString(), symbols[renames[n]]);
         }
       }
     }
 
-    String output = outputCollector.getOutput('', 'dart');
+    String output = compiler.assembledCode;
     String getNameMatch = MirrorRenamerImpl.MIRROR_HELPER_GET_NAME_FUNCTION;
     Iterable i = getNameMatch.allMatches(output);
     print(output);
     if (minify) {
       Expect.equals(0, i.length);
     } else {
       // Appears twice in code (defined & called).
       Expect.equals(2, i.length);
     }
 
@@ skipping 21 matching lines @@
 class Foo {
   noSuchMethod(Invocation invocation) {
     MirrorSystem.getName(invocation.memberName);
   }
 }
 
 void main() {
   new Foo().fisk();
 }
 """};