move V2 classes in chrome/engine to syncer_v2 namespace

sync/internal_api/public/sync_context.h

Index: sync/internal_api/public/sync_context.h
diff --git a/sync/internal_api/public/sync_context.h b/sync/internal_api/public/sync_context.h
index 98740e19b9dc88310c5a43345e204526747d02a2..40254b5ddda040307a20b4bad695a31b80b70c49 100644
--- a/sync/internal_api/public/sync_context.h
+++ b/sync/internal_api/public/sync_context.h
@@ -12,11 +12,9 @@
 #include "sync/internal_api/public/base/model_type.h"
 #include "sync/internal_api/public/non_blocking_sync_common.h"
 
-namespace syncer {
+namespace syncer_v2 {
 class ModelTypeSyncProxyImpl;
-}
 
-namespace syncer_v2 {
 // An interface of the core parts of sync.
 //
 // In theory, this is the component that provides off-thread sync types with
@@ -38,7 +36,7 @@ class SYNC_EXPORT_PRIVATE SyncContext {
       const DataTypeState& data_type_state,
       const UpdateResponseDataList& saved_pending_updates,
       const scoped_refptr<base::SequencedTaskRunner>& datatype_task_runner,
-      const base::WeakPtr<syncer::ModelTypeSyncProxyImpl>& type_sync_proxy) = 0;
+      const base::WeakPtr<ModelTypeSyncProxyImpl>& type_sync_proxy) = 0;
 
   // Disconnects the syncer from the model and stops syncing the type.
   //