Add string mapping for INVALIDATOR_SHUTTING_DOWN.

components/invalidation/public/invalidator_state.cc

 // 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.
 
 #include "components/invalidation/public/invalidator_state.h"
 
 #include "base/logging.h"
 
 namespace syncer {
 
 const char* InvalidatorStateToString(InvalidatorState state) {
   switch (state) {
     case TRANSIENT_INVALIDATION_ERROR:
       return "TRANSIENT_INVALIDATION_ERROR";
     case INVALIDATION_CREDENTIALS_REJECTED:
       return "INVALIDATION_CREDENTIALS_REJECTED";
     case INVALIDATIONS_ENABLED:
       return "INVALIDATIONS_ENABLED";
+    case INVALIDATOR_SHUTTING_DOWN:
+      return "INVALIDATOR_SHUTTING_DOWN";
     default:
       NOTREACHED();
       return "UNKNOWN_INVALIDATOR_STATE";
   }
 }
 
 }  // namespace syncer