Revert "Move dart2js from sdk/lib/_internal/compiler to pkg/compiler"

tests/compiler/dart2js/mirror_system_helper.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.
 
 library mirror_system_helper;
 
 import 'dart:async';
-import 'package:compiler/src/mirrors/source_mirrors.dart';
-import 'package:compiler/src/mirrors/dart2js_mirrors.dart';
+import 'package:compiler/implementation/mirrors/source_mirrors.dart';
+import 'package:compiler/implementation/mirrors/dart2js_mirrors.dart';
 import 'mock_compiler.dart';
 
-export 'package:compiler/src/mirrors/source_mirrors.dart';
-export 'package:compiler/src/mirrors/mirrors_util.dart';
+export 'package:compiler/implementation/mirrors/source_mirrors.dart';
+export 'package:compiler/implementation/mirrors/mirrors_util.dart';
 
 const String SOURCE = 'source';
 final Uri SOURCE_URI = new Uri(scheme: SOURCE, path: SOURCE);
 
 // TODO(johnniwinther): Move this to a mirrors helper library.
 Future<MirrorSystem> createMirrorSystem(String source) {
   MockCompiler compiler = new MockCompiler.internal(
       analyzeOnly: true,
       analyzeAll: true,
       preserveComments: true);
@@ skipping 106 matching lines @@
   if (expected.length != types.length) return false;
   Iterator<TypeMirror> expectedIterator = expected.iterator;
   Iterator<TypeMirror> typesIterator = types.iterator;
   while (expectedIterator.moveNext() && typesIterator.moveNext()) {
     if (!check(expectedIterator.current, typesIterator.current)) {
       return false;
     }
   }
   return true;
 }