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

pkg/polymer/e2e_test/experimental_boot/lib/b.dart

Index: pkg/polymer/e2e_test/experimental_boot/lib/b.dart
diff --git a/pkg/polymer/example/canonicalization/lib/b.dart b/pkg/polymer/e2e_test/experimental_boot/lib/b.dart
similarity index 82%
rename from pkg/polymer/example/canonicalization/lib/b.dart
rename to pkg/polymer/e2e_test/experimental_boot/lib/b.dart
index fbdccf604595572141e69ad29d5183be5b811b4f..cbcfa0f70852349c8f796d3681fb6a2d7e18c468 100644
--- a/pkg/polymer/example/canonicalization/lib/b.dart
+++ b/pkg/polymer/e2e_test/experimental_boot/lib/b.dart
@@ -2,10 +2,10 @@
 // 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.b;
+library experimental_boot.b;
 
 import 'package:polymer/polymer.dart';
-import 'package:canonicalization/c.dart';
+import 'package:experimental_boot/c.dart';
 import 'd.dart';
 
 int b = 0;