[GCM] Update ResetStore histograms

components/gcm_driver/gcm_client_impl.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef COMPONENTS_GCM_DRIVER_GCM_CLIENT_IMPL_H_
 #define COMPONENTS_GCM_DRIVER_GCM_CLIENT_IMPL_H_
 
 #include <stdint.h>
 
 #include <map>
@@ skipping 157 matching lines @@
     // True if accounts were already provided through SetAccountsForCheckin(),
     // or when |last_checkin_accounts| was loaded as empty.
     bool accounts_set;
     // Map of account email addresses and OAuth2 tokens that will be sent to the
     // checkin server on a next checkin.
     std::map<std::string, std::string> account_tokens;
     // As set of accounts last checkin was completed with.
     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.
   using PendingRegistrationRequests =
       std::map<linked_ptr<RegistrationInfo>,
                std::unique_ptr<RegistrationRequest>,
                RegistrationInfoComparer>;
 
   // Collection of pending unregistration requests. Keys are RegistrationInfo
   // instance, while values are pending unregistration requests to disable the
@@ skipping 196 matching lines @@
 
   // Factory for creating references in callbacks.
   base::WeakPtrFactory<GCMClientImpl> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(GCMClientImpl);
 };
 
 }  // namespace gcm
 
 #endif  // COMPONENTS_GCM_DRIVER_GCM_CLIENT_IMPL_H_