Notify GCMAppHandlers when the store is reset, so they clear cached IDs

components/gcm_driver/gcm_client.h

Index: components/gcm_driver/gcm_client.h
diff --git a/components/gcm_driver/gcm_client.h b/components/gcm_driver/gcm_client.h
index 3e399c561f8610b7f63375983040c5d4e790d87a..6a7910ea528786a3d88fb6dfcb03096bc7232ec6 100644
--- a/components/gcm_driver/gcm_client.h
+++ b/components/gcm_driver/gcm_client.h
@@ -212,6 +212,10 @@ class GCMClient {
 
     // Called when the connection is interrupted.
     virtual void OnDisconnected() = 0;
+
+    // Called when the GCM store is reset (e.g. due to corruption), which
+    // changes the device ID, invalidating all prior registrations.
+    virtual void OnStoreReset() = 0;
   };
 
   GCMClient();