move V2 classes in chrome/engine to syncer_v2 namespace

sync/internal_api/public/sync_context_proxy.h

Index: sync/internal_api/public/sync_context_proxy.h
diff --git a/sync/internal_api/public/sync_context_proxy.h b/sync/internal_api/public/sync_context_proxy.h
index 94c7bc379e69f8bdd90c3d29691cd6b2ba535a0a..1a0fec16d599bf0d347d38d4863f34e0e92b8801 100644
--- a/sync/internal_api/public/sync_context_proxy.h
+++ b/sync/internal_api/public/sync_context_proxy.h
@@ -9,11 +9,8 @@
 #include "sync/internal_api/public/base/model_type.h"
 #include "sync/internal_api/public/non_blocking_sync_common.h"
 
-namespace syncer {
-class ModelTypeSyncProxyImpl;
-}
-
 namespace syncer_v2 {
+class ModelTypeSyncProxyImpl;
 
 // Interface for the datatype integration logic from non-sync threads.
 //
@@ -30,7 +27,7 @@ class SYNC_EXPORT_PRIVATE SyncContextProxy {
       syncer::ModelType type,
       const DataTypeState& data_type_state,
       const UpdateResponseDataList& saved_pending_updates,
-      const base::WeakPtr<syncer::ModelTypeSyncProxyImpl>& type_sync_proxy) = 0;
+      const base::WeakPtr<ModelTypeSyncProxyImpl>& type_sync_proxy) = 0;
 
   // Tells the syncer that we're no longer interested in syncing this type.
   //