Replace bootstrap logic with 'boot.js', use 'component/dart' mime-type and add

pkg/polymer/test/attr_deserialize_test.dart

Index: pkg/polymer/test/attr_deserialize_test.dart
diff --git a/pkg/polymer/test/attr_deserialize_test.dart b/pkg/polymer/test/attr_deserialize_test.dart
index 536b0196a5216878452e26ae3f561da34488c480..55060e1c113d769a2ac61224016e88693c9659e8 100644
--- a/pkg/polymer/test/attr_deserialize_test.dart
+++ b/pkg/polymer/test/attr_deserialize_test.dart
@@ -19,8 +19,8 @@ class MyElement extends PolymerElement {
   @published Object json;
 }
 
+@initMethod
 main() {
-  initPolymer();
   useHtmlConfiguration();
 
   setUp(() => Polymer.onReady);