[Sync] Move sync/{internal_api,syncable} into syncer namespace

sync/engine/process_updates_command.h

Index: sync/engine/process_updates_command.h
diff --git a/sync/engine/process_updates_command.h b/sync/engine/process_updates_command.h
index 6aeb1819b37f0aa997c0c9d882b1890201276dd3..9ec9b31abebf65a170d4266ab72f2e1962e20115 100644
--- a/sync/engine/process_updates_command.h
+++ b/sync/engine/process_updates_command.h
@@ -10,16 +10,16 @@
 #include "sync/engine/model_changing_syncer_command.h"
 #include "sync/engine/syncer_types.h"
 
-namespace syncable {
-class WriteTransaction;
-}
-
 namespace sync_pb {
 class SyncEntity;
 }
 
 namespace syncer {
 
+namespace syncable {
+class WriteTransaction;
+}
+
 class Cryptographer;
 
 // A syncer command for processing updates.