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

sync/syncable/mutable_entry.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef SYNC_SYNCABLE_MUTABLE_ENTRY_H_
 #define SYNC_SYNCABLE_MUTABLE_ENTRY_H_
 #pragma once
 
 #include "sync/syncable/entry.h"
 #include "sync/syncable/metahandle_set.h"
 
 namespace syncer {
 class WriteNode;
-}
 
 namespace syncable {
 
 class WriteTransaction;
 
 enum Create {
   CREATE
 };
 
 enum CreateNewUpdateItem {
@@ skipping 83 matching lines @@
  protected:
   MutableEntry();
 
   DISALLOW_COPY_AND_ASSIGN(MutableEntry);
 };
 
 // This function sets only the flags needed to get this entry to sync.
 bool MarkForSyncing(syncable::MutableEntry* e);
 
 }  // namespace syncable
+}  // namespace syncer
 
 #endif  // SYNC_SYNCABLE_MUTABLE_ENTRY_H_