Push API: Prevent DCHECK when clear permissions after clear SW DB

chrome/browser/push_messaging/push_messaging_service_impl.cc

Index: chrome/browser/push_messaging/push_messaging_service_impl.cc
diff --git a/chrome/browser/push_messaging/push_messaging_service_impl.cc b/chrome/browser/push_messaging/push_messaging_service_impl.cc
index da017ae9308b3500412c942cf04f82253c41560d..20c0597fe46b2772df74f93fefa1a69a73d71961 100644
--- a/chrome/browser/push_messaging/push_messaging_service_impl.cc
+++ b/chrome/browser/push_messaging/push_messaging_service_impl.cc
@@ -649,8 +649,12 @@ void PushMessagingServiceImpl::Unregister(
                  was_registered, callback);
 #if defined(OS_ANDROID)
   // On Android the backend is different, and requires the original sender_id.
-  GetGCMDriver()->UnregisterWithSenderId(app_id_guid, sender_id,
-                                         unregister_callback);
+  // UnregisterBecausePermissionRevoked sometimes calls us with an empty one.
+  if (sender_id.empty())
+    unregister_callback.Run(gcm::GCMClient::INVALID_PARAMETER);
+  else
+    GetGCMDriver()->UnregisterWithSenderId(app_id_guid, sender_id,
+                                           unregister_callback);
 #else
   GetGCMDriver()->Unregister(app_id_guid, unregister_callback);
 #endif
@@ -741,6 +745,12 @@ void PushMessagingServiceImpl::UnregisterBecausePermissionRevoked(
   base::Closure barrier_closure = base::BarrierClosure(2, closure);
 
   // Unregister the PushMessagingApplicationId with the push service.
+  // It's possible for GetSenderId to have failed and sender_id to be empty, if
+  // cookies (and the SW database) for an origin got cleared before permissions
+  // are cleared for the origin. In that case Unregister will just delete the
+  // application ID to block future messages.
+  // TODO(johnme): Auto-unregister before SW DB is cleared
+  // (https://crbug.com/402458).
   Unregister(id.app_id_guid(), sender_id,
              base::Bind(&UnregisterCallbackToClosure, barrier_closure));