Revert "Move dart2jslib parts into separate libraries."

pkg/compiler/lib/src/dart_backend/dart_backend.dart

 // Copyright (c) 2012, 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 dart_backend;
 
 import 'dart:async' show Future;
 import 'dart:math' show max;
-
-import '../../compiler.dart' show CompilerOutputProvider;
 import '../elements/elements.dart';
 import '../dart2jslib.dart';
+import '../library_loader.dart' show LoadedLibraries;
 import '../dart_types.dart';
-import '../diagnostic_listener.dart';
+import '../tree/tree.dart';
 import '../compile_time_constants.dart';
 import '../constants/constant_system.dart';
 import '../constants/expressions.dart';
 import '../constants/values.dart';
-import '../enqueue.dart' show
-    Enqueuer,
-    ResolutionEnqueuer,
-    WorldImpact;
-import '../library_loader.dart' show LoadedLibraries;
-import '../messages.dart' show MessageKind;
+import '../universe/universe.dart' show UniverseSelector;
+import '../util/util.dart';
 import '../mirror_renamer/mirror_renamer.dart';
-import '../resolution/resolution.dart' show
-    TreeElements,
-    TreeElementMapping;
-import '../scanner/scannerlib.dart' show
-    StringToken,
-    Keyword,
-    OPEN_PAREN_INFO,
-    CLOSE_PAREN_INFO,
-    SEMICOLON_INFO,
-    IDENTIFIER_INFO;
-import '../tree/tree.dart';
-import '../universe/universe.dart' show
-    Selector,
-    UniverseSelector;
-import '../util/util.dart';
 import 'backend_ast_to_frontend_ast.dart' as backend2frontend;
+import '../../compiler.dart' show CompilerOutputProvider;
+
+import '../scanner/scannerlib.dart' show StringToken,
+                                         Keyword,
+                                         OPEN_PAREN_INFO,
+                                         CLOSE_PAREN_INFO,
+                                         SEMICOLON_INFO,
+                                         IDENTIFIER_INFO;
 
 part 'backend.dart';
 part 'renamer.dart';
 part 'placeholder_collector.dart';
 part 'outputter.dart';