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

pkg/compiler/lib/src/js_backend/js_backend.dart

Index: pkg/compiler/lib/src/js_backend/js_backend.dart
diff --git a/pkg/compiler/lib/src/js_backend/js_backend.dart b/pkg/compiler/lib/src/js_backend/js_backend.dart
deleted file mode 100644
index 0f9f0ce1c6a3089a18388be6df7a69787e570177..0000000000000000000000000000000000000000
--- a/pkg/compiler/lib/src/js_backend/js_backend.dart
+++ /dev/null
@@ -1,44 +0,0 @@
-// 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 js_backend;
-
-import 'dart:async' show EventSink, Future;
-import 'dart:collection' show Queue, LinkedHashMap, LinkedHashSet;
-
-import 'package:_internal/compiler/js_lib/shared/embedded_names.dart' as embeddedNames;
-
-import '../closure.dart';
-import '../constants/expressions.dart';
-import '../constants/values.dart';
-import '../dart2jslib.dart';
-import '../dart_types.dart';
-import '../elements/elements.dart';
-import '../js/js.dart' as jsAst;
-import '../js/js.dart' show js;
-import '../js_emitter/js_emitter.dart'
-    show Emitter, CodeEmitterTask, ClassBuilder, MetadataEmitter;
-import '../library_loader.dart' show LibraryLoader;
-import '../native/native.dart' as native;
-import '../ssa/ssa.dart';
-import '../tree/tree.dart';
-import '../types/types.dart';
-import '../universe/universe.dart';
-import '../util/characters.dart';
-import '../util/util.dart';
-
-import '../elements/visitor.dart' show
-    ElementVisitor;
-
-part 'backend.dart';
-part 'checked_mode_helpers.dart';
-part 'constant_emitter.dart';
-part 'constant_handler_javascript.dart';
-part 'constant_system_javascript.dart';
-part 'custom_elements_analysis.dart';
-part 'minify_namer.dart';
-part 'namer.dart';
-part 'native_emitter.dart';
-part 'runtime_types.dart';
-part 'type_variable_handler.dart';