Add JavaScript AST.

lib/compiler/implementation/js/js.dart

Index: lib/compiler/implementation/js/js.dart
diff --git a/lib/compiler/implementation/dart_backend/dart_backend.dart b/lib/compiler/implementation/js/js.dart
similarity index 57%
copy from lib/compiler/implementation/dart_backend/dart_backend.dart
copy to lib/compiler/implementation/js/js.dart
index 0d5cc1bd6f44d51e1d092662cccd01a063e0b139..731690ecb634c5d8ce5f5c7a4e76f02ff8fd0a4f 100644
--- a/lib/compiler/implementation/dart_backend/dart_backend.dart
+++ b/lib/compiler/implementation/js/js.dart
@@ -2,11 +2,13 @@
 // 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');
+#library('js');
 
-#import('../elements/elements.dart');
+#import("precedence.dart");
+
+// TODO(floitsch): remove this dependency (currently necessary for the
+// CodeBuffer).
 #import('../leg.dart');
-#import('../tree/tree.dart');
 
-#source('backend.dart');
-#source('emitter.dart');
+#source('nodes.dart');
+#source('printer.dart');