Bring back initPolymer, allow boot.js only if using "polymer_experimental.html".

pkg/polymer/e2e_test/bad_import3/lib/a.dart

Index: pkg/polymer/e2e_test/bad_import3/lib/a.dart
diff --git a/pkg/polymer/example/canonicalization2/lib/a.dart b/pkg/polymer/e2e_test/bad_import3/lib/a.dart
similarity index 74%
copy from pkg/polymer/example/canonicalization2/lib/a.dart
copy to pkg/polymer/e2e_test/bad_import3/lib/a.dart
index dfbe3cae43697d624ce34f47d216e2f2010ccd94..a0a05cbbd3e000710792c67ad58a85407aee6260 100644
--- a/pkg/polymer/example/canonicalization2/lib/a.dart
+++ b/pkg/polymer/e2e_test/bad_import3/lib/a.dart
@@ -2,15 +2,11 @@
 // 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 canonicalization.a;
+library bad_import3.a;
 
 import 'package:polymer/polymer.dart';
-import 'package:canonicalization/c.dart';
-import 'd.dart';
 
 int a = 0;
 @initMethod initA() {
   a++;
-  c++;
-  d++;
 }