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

dart/samples/ui_lib/observable/observable.dart

Index: dart/samples/ui_lib/observable/observable.dart
diff --git a/dart/samples/ui_lib/observable/observable.dart b/dart/samples/ui_lib/observable/observable.dart
index 739e5faa17ea98d5e7fd193f4deb1f42f6e75590..41e0e03c7d290c62de165b79632c9be7a8fc66e5 100644
--- a/dart/samples/ui_lib/observable/observable.dart
+++ b/dart/samples/ui_lib/observable/observable.dart
@@ -2,12 +2,12 @@
 // 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 observable;
+#library('observable');
 
-import 'dart:coreimpl';
+#import('dart:coreimpl');
 
-part 'ChangeEvent.dart';
-part 'EventBatch.dart';
+#source('ChangeEvent.dart');
+#source('EventBatch.dart');
 
 /**
  * An object whose changes are tracked and who can issue events notifying how it