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

pkg/docgen/lib/src/generator.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.
 
 library docgen.generator;
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:convert';
 import 'dart:io';
 
 import 'package:markdown/markdown.dart' as markdown;
 import 'package:path/path.dart' as path;
 
 import 'package:compiler/compiler.dart' as api;
-import 'package:compiler/src/filenames.dart';
-import 'package:compiler/src/mirrors/analyze.dart'
+import 'package:compiler/implementation/filenames.dart';
+import 'package:compiler/implementation/mirrors/analyze.dart'
     as dart2js;
-import 'package:compiler/src/source_file_provider.dart';
+import 'package:compiler/implementation/source_file_provider.dart';
 
 import 'exports/dart2js_mirrors.dart' as dart2js_mirrors;
 import 'exports/libraries.dart';
 import 'exports/mirrors_util.dart' as dart2js_util;
 import 'exports/source_mirrors.dart';
 
 import 'io.dart';
 import 'library_helpers.dart';
 import 'models.dart';
 import 'package_helpers.dart';
@@ skipping 444 matching lines @@
   * [Samples](http://www.dartlang.org/samples/)
   * [A Tour of the Dart Libraries](http://www.dartlang.org/docs/dart-up-and-running/contents/ch03.html)
 
 This API reference is automatically generated from the source code in the
 [Dart project](https://code.google.com/p/dart/).
 If you'd like to contribute to this documentation, see
 [Contributing](https://code.google.com/p/dart/wiki/Contributing)
 and
 [Writing API Documentation](https://code.google.com/p/dart/wiki/WritingApiDocumentation).
 """;