[Sync] Fix test support targets + duplicate namespaces.

components/sync/device_info/device_info_service.h

Index: components/sync/device_info/device_info_service.h
diff --git a/components/sync/device_info/device_info_service.h b/components/sync/device_info/device_info_service.h
index 14eb24d2a0956932889adbbb0c02bfe0c6d25129..700ed1fd26e70853e131192698c65f25016d0a19 100644
--- a/components/sync/device_info/device_info_service.h
+++ b/components/sync/device_info/device_info_service.h
@@ -23,20 +23,15 @@
 #include "components/sync/model/model_type_store.h"
 #include "components/sync/model/simple_metadata_change_list.h"
 
-namespace syncer {
-class SyncError;
-}  // namespace syncer
-
-namespace syncer {
-class ModelTypeChangeProcessor;
-}  // namespace syncer
-
 namespace sync_pb {
 class DeviceInfoSpecifics;
 }  // namespace sync_pb
 
 namespace syncer {
 
+class ModelTypeChangeProcessor;
+class SyncError;
+
 // USS service implementation for DEVICE_INFO model type. Handles storage of
 // device info and associated sync metadata, applying/merging foreign changes,
 // and allows public read access.