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

sync/engine/update_applicator.h

Index: sync/engine/update_applicator.h
diff --git a/sync/engine/update_applicator.h b/sync/engine/update_applicator.h
index de059993c758cd608d1d7f1e75753308764c9eb9..ea16fa24840f5b17d1ad79c57fb91af2f1c37c67 100644
--- a/sync/engine/update_applicator.h
+++ b/sync/engine/update_applicator.h
@@ -19,11 +19,6 @@
 #include "sync/internal_api/public/engine/model_safe_worker.h"
 #include "sync/syncable/syncable_id.h"
 
-namespace syncable {
-class WriteTransaction;
-class Entry;
-}
-
 namespace syncer {
 
 namespace sessions {
@@ -31,6 +26,11 @@ class ConflictProgress;
 class UpdateProgress;
 }
 
+namespace syncable {
+class WriteTransaction;
+class Entry;
+}
+
 class ConflictResolver;
 class Cryptographer;