Revert "Parts must start with 'part of'" and "Attempt to fix VM build"

dart/lib/compiler/implementation/dart_backend/backend.dart

Index: dart/lib/compiler/implementation/dart_backend/backend.dart
diff --git a/dart/lib/compiler/implementation/dart_backend/backend.dart b/dart/lib/compiler/implementation/dart_backend/backend.dart
index 0bc897d214f9c1fa3b1b292572df8268894ab792..45eef3fd8c951a3f3a7e5e659df9814f174f7570 100644
--- a/dart/lib/compiler/implementation/dart_backend/backend.dart
+++ b/dart/lib/compiler/implementation/dart_backend/backend.dart
@@ -2,8 +2,6 @@
 // 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.
 
-part of dart_backend;
-
 class ElementAst {
   final Node ast;
   final TreeElements treeElements;