Define PushMessagingApplicationId and replace ad-hoc code.

content/browser/push_messaging_message_filter.cc

Index: content/browser/push_messaging_message_filter.cc
diff --git a/content/browser/push_messaging_message_filter.cc b/content/browser/push_messaging_message_filter.cc
index f34ffb2ad1fee39745d817a691f06ec54846c72f..fc6b73bee0dcb1ae1c4669e456bb2860b4d53a21 100644
--- a/content/browser/push_messaging_message_filter.cc
+++ b/content/browser/push_messaging_message_filter.cc
@@ -13,6 +13,7 @@
 #include "content/common/push_messaging_messages.h"
 #include "content/public/browser/browser_context.h"
 #include "content/public/browser/browser_thread.h"
+#include "content/public/browser/push_messaging_application_id.h"
 #include "content/public/browser/push_messaging_service.h"
 
 namespace content {
@@ -84,10 +85,10 @@ void PushMessagingMessageFilter::DoRegister(
         PUSH_MESSAGING_STATUS_REGISTRATION_FAILED_SERVICE_NOT_AVAILABLE));
     return;
   }
-  // TODO(mvanouwerkerk): Is this the app_id format we want to use?
-  std::string app_id =
-      origin.spec() + " " + base::Int64ToString(service_worker_registration_id);
-  service()->Register(app_id,
+  PushMessagingApplicationId application_id =
+      PushMessagingApplicationId(origin, service_worker_registration_id);
+  DCHECK(application_id.is_valid());
+  service()->Register(application_id.ToString(),
                       sender_id,
                       render_process_id_,
                       render_frame_id,