Add testing for subscription from service workers

content/renderer/push_messaging/push_messaging_dispatcher.cc

Index: content/renderer/push_messaging/push_messaging_dispatcher.cc
diff --git a/content/renderer/push_messaging/push_messaging_dispatcher.cc b/content/renderer/push_messaging/push_messaging_dispatcher.cc
index f505f93ed80e2858c01d844283293b7e76b93b5b..0bd40dc69bb480abe3dd8bf88c1098ff395800a7 100644
--- a/content/renderer/push_messaging/push_messaging_dispatcher.cc
+++ b/content/renderer/push_messaging/push_messaging_dispatcher.cc
@@ -55,7 +55,9 @@ void PushMessagingDispatcher::subscribe(
   } else {
     PushSubscriptionOptions content_options;
     content_options.user_visible_only = options.userVisibleOnly;
-    content_options.sender_info = options.applicationServerKey.utf8();
+    // Just treat the server key as a string of bytes and pass it to the push
+    // service.
+    content_options.sender_info = options.applicationServerKey.latin1();
     DoSubscribe(service_worker_registration, content_options, callbacks);
   }
 }