Ensure we run the observable transform on PolymerElement (fixes issue 14942)

pkg/polymer/lib/transformer.dart

 // Copyright (c) 2013, 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.
 
 /** Transfomer used for pub-serve and pub-deploy. */
 library polymer.transformer;
 
 import 'package:barback/barback.dart';
-import 'package:observe/transform.dart';
+import 'package:observe/transformer.dart';
 import 'src/build/code_extractor.dart';
 import 'src/build/import_inliner.dart';
 import 'src/build/script_compactor.dart';
 import 'src/build/polyfill_injector.dart';
 import 'src/build/common.dart';
 
 /**
  * The Polymer transformer, which internally runs several phases that will:
  *   * Extract inlined script tags into their separate files
  *   * Apply the observable transformer on every Dart script.
@@ skipping 46 matching lines @@
 
 List<List<Transformer>> _createDeployPhases(TransformOptions options) {
   return [
     [new InlineCodeExtractor(options)],
     [new ObservableTransformer()],
     [new ImportInliner(options)],
     [new ScriptCompactor(options)],
     [new PolyfillInjector(options)]
   ];
 }