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

components/sync/device_info/device_info_service_unittest.cc

Index: components/sync/device_info/device_info_service_unittest.cc
diff --git a/components/sync/device_info/device_info_service_unittest.cc b/components/sync/device_info/device_info_service_unittest.cc
index 83a9c8d4e55a32dd1f696f5fde7bf3a0277fe549..4b5d9b30eae570bf431b1116172392f1b8500e99 100644
--- a/components/sync/device_info/device_info_service_unittest.cc
+++ b/components/sync/device_info/device_info_service_unittest.cc
@@ -338,7 +338,7 @@ TEST_F(DeviceInfoServiceTest, LocalProviderSubscription) {
 
 // Metadata shouldn't be loaded before the provider is initialized.
 TEST_F(DeviceInfoServiceTest, LocalProviderInitRace) {
-  set_local_device(base::WrapUnique(new LocalDeviceInfoProviderMock()));
+  set_local_device(base::MakeUnique<LocalDeviceInfoProviderMock>());
   InitializeAndPump();
   EXPECT_FALSE(processor()->metadata());
 
@@ -731,6 +731,24 @@ TEST_F(DeviceInfoServiceTest, CountActiveDevices) {
   EXPECT_EQ(2, service()->CountActiveDevices());
 }
 
+TEST_F(DeviceInfoServiceTest, MultipleOnProviderInitialized) {
+  set_local_device(base::MakeUnique<LocalDeviceInfoProviderMock>());
+  InitializeAndPump();
+  EXPECT_EQ(nullptr, processor()->metadata());
+
+  // Verify the processor was given metadata.
+  local_device()->Initialize(CreateDeviceInfo());
+  base::RunLoop().RunUntilIdle();
+  const MetadataBatch* metadata = processor()->metadata();
+  EXPECT_NE(nullptr, metadata);
+
+  // Pointer address of metadata should remain constant because the processor
+  // should not have been given new metadata.
+  local_device()->Initialize(CreateDeviceInfo());
+  base::RunLoop().RunUntilIdle();
+  EXPECT_EQ(metadata, processor()->metadata());
+}
+
 }  // namespace
 
 }  // namespace syncer