[Sync] Avoid sending the processor metadata again on re-enabling sync.

components/sync/device_info/device_info_service.cc

 // Copyright 2015 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/sync/device_info/device_info_service.h"
 
 #include <algorithm>
 #include <set>
 #include <utility>
 
@@ skipping 259 matching lines @@
              << " with ID " << guid;
     store_->DeleteData(batch, guid);
     all_data_.erase(iter);
     return true;
   } else {
     return false;
   }
 }
 
 void DeviceInfoService::OnProviderInitialized() {
+  // Now that the provider has initialized, remove the subscription. The service
+  // should only need to give the processor metadata upon initialization. If
+  // sync is disabled and enabled, our provider will try to retrigger this
+  // event, but we do not want to send any more metadata to the processor.
+  subscription_.reset();
+
   has_provider_initialized_ = true;
   LoadMetadataIfReady();
 }
 
 void DeviceInfoService::OnStoreCreated(Result result,
                                        std::unique_ptr<ModelTypeStore> store) {
   if (result == Result::SUCCESS) {
     std::swap(store_, store);
     store_->ReadAllData(
         base::Bind(&DeviceInfoService::OnReadAllData, base::AsWeakPtr(this)));
@@ skipping 170 matching lines @@
 Time DeviceInfoService::GetLastUpdateTime(
     const DeviceInfoSpecifics& specifics) {
   if (specifics.has_last_updated_timestamp()) {
     return ProtoTimeToTime(specifics.last_updated_timestamp());
   } else {
     return Time();
   }
 }
 
 }  // namespace syncer