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

pkg/polymer/example/canonicalization/lib/d.dart

Index: pkg/polymer/example/canonicalization/lib/d.dart
diff --git a/pkg/polymer/example/canonicalization/lib/d.dart b/pkg/polymer/example/canonicalization/lib/d.dart
deleted file mode 100644
index 7d2a58e0c0cada0a63a591a437961a1057922541..0000000000000000000000000000000000000000
--- a/pkg/polymer/example/canonicalization/lib/d.dart
+++ /dev/null
@@ -1,7 +0,0 @@
-// 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.
-
-library canonicalization.d;
-
-int d = 0;