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

components/proximity_auth/cryptauth/cryptauth_gcm_manager_impl.cc

Index: components/proximity_auth/cryptauth/cryptauth_gcm_manager_impl.cc
diff --git a/components/proximity_auth/cryptauth/cryptauth_gcm_manager_impl.cc b/components/proximity_auth/cryptauth/cryptauth_gcm_manager_impl.cc
index 77680e8f31f40be707e320f2f0acdb05c644797b..9331e2737d122450efcab5864d84fb7ae3eb7607 100644
--- a/components/proximity_auth/cryptauth/cryptauth_gcm_manager_impl.cc
+++ b/components/proximity_auth/cryptauth/cryptauth_gcm_manager_impl.cc
@@ -83,6 +83,12 @@ void CryptAuthGCMManagerImpl::RemoveObserver(Observer* observer) {
 void CryptAuthGCMManagerImpl::ShutdownHandler() {
 }
 
+void CryptAuthGCMManagerImpl::OnStoreReset() {
+  // We will automatically re-register to GCM and re-enroll the new registration
+  // ID to Cryptauth during the next scheduled sync.
+  pref_service_->ClearPref(prefs::kCryptAuthGCMRegistrationId);
+}
+
 void CryptAuthGCMManagerImpl::OnMessage(const std::string& app_id,
                                         const gcm::IncomingMessage& message) {
   std::vector<std::string> fields;