Move nullable_string16.h to the string subdirectory.

content/common/dom_storage_messages.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.
 
 // Multiply-included message file, no traditional include guard.
 #include "content/public/common/common_param_traits.h"
 #include "googleurl/src/gurl.h"
 #include "ipc/ipc_message_macros.h"
 #include "ipc/ipc_param_traits.h"
 #include "third_party/WebKit/public/platform/WebStorageArea.h"
 #include "webkit/common/dom_storage/dom_storage_types.h"
 
 #define IPC_MESSAGE_START DOMStorageMsgStart
 
 // Signals a local storage event.
 IPC_STRUCT_BEGIN(DOMStorageMsg_Event_Params)
   // The key that generated the storage event.  Null if clear() was called.
-  IPC_STRUCT_MEMBER(NullableString16, key)
+  IPC_STRUCT_MEMBER(base::NullableString16, key)
 
   // The old value of this key.  Null on clear() or if it didn't have a value.
-  IPC_STRUCT_MEMBER(NullableString16, old_value)
+  IPC_STRUCT_MEMBER(base::NullableString16, old_value)
 
   // The new value of this key.  Null on removeItem() or clear().
-  IPC_STRUCT_MEMBER(NullableString16, new_value)
+  IPC_STRUCT_MEMBER(base::NullableString16, new_value)
 
   // The origin this is associated with.
   IPC_STRUCT_MEMBER(GURL, origin)
 
   // The URL of the page that caused the storage event.
   IPC_STRUCT_MEMBER(GURL, page_url)
 
   // The non-zero connection_id which caused the event or 0 if the event
   // was not caused by the target renderer process.
   IPC_STRUCT_MEMBER(int, connection_id)
@@ skipping 51 matching lines @@
                      string16 /* key */,
                      GURL /* page_url */)
 
 // Clear the storage area. A completion notification is sent in response.
 IPC_MESSAGE_CONTROL2(DOMStorageHostMsg_Clear,
                      int /* connection_id */,
                      GURL /* page_url */)
 
 // Used to flush the ipc message queue.
 IPC_SYNC_MESSAGE_CONTROL0_0(DOMStorageHostMsg_FlushMessages)