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

components/sync/device_info/device_info_service.cc

Index: components/sync/device_info/device_info_service.cc
diff --git a/components/sync/device_info/device_info_service.cc b/components/sync/device_info/device_info_service.cc
index b13f1d4e5d4db5d372cac9ead0d2e6eff0882c77..f00c6c8ea4114464ca896f7c6488b179e61989b7 100644
--- a/components/sync/device_info/device_info_service.cc
+++ b/components/sync/device_info/device_info_service.cc
@@ -277,6 +277,12 @@ bool DeviceInfoService::DeleteSpecifics(const std::string& guid,
 }
 
 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();
 }