[GCM] Update ResetStore histograms

components/gcm_driver/gcm_client_impl.h

Index: components/gcm_driver/gcm_client_impl.h
diff --git a/components/gcm_driver/gcm_client_impl.h b/components/gcm_driver/gcm_client_impl.h
index dcda57db288946f2086be305cbdbe23ce51c5969..6700e0c7e0b5ddde0560b009ce18c95f89f81776 100644
--- a/components/gcm_driver/gcm_client_impl.h
+++ b/components/gcm_driver/gcm_client_impl.h
@@ -175,6 +175,16 @@ class GCMClientImpl
     std::set<std::string> last_checkin_accounts;
   };
 
+  // Reasons for resetting the GCM Store.
+  // Note: this enum is recorded into a histogram. Do not change enum value
+  // or order.
+  enum ResetReason {
+    LOAD_FAILURE,      // GCM store failed to load, but the store exists.
+    CHECKIN_REJECTED,  // Checkin was rejected by server.
+
+    RESET_REASON_COUNT,
+  };
+
   // Collection of pending registration requests. Keys are RegistrationInfo
   // instance, while values are pending registration requests to obtain a
   // registration ID for requesting application.
@@ -220,7 +230,7 @@ class GCMClientImpl
   // Starts a login on mcs_client_.
   void StartMCSLogin();
   // Resets the GCM store when it is corrupted.
-  void ResetStore();
+  void ResetStore(ResetReason reset_reason);
   // Sets state to ready. This will initiate the MCS login and notify the
   // delegates.
   void OnReady(const std::vector<AccountMapping>& account_mappings,