Move nullable_string16.h to the string subdirectory.

webkit/common/webdropdata.h

 // Copyright 2013 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.
 //
 // A struct for managing data being dropped on a webview.  This represents a
 // union of all the types of data that can be dropped in a platform neutral
 // way.
 
 #ifndef WEBKIT_COMMON_WEBDROPDATA_H_
 #define WEBKIT_COMMON_WEBDROPDATA_H_
 
 #include <map>
 #include <string>
 #include <vector>
 
-#include "base/nullable_string16.h"
+#include "base/strings/nullable_string16.h"
 #include "base/strings/string16.h"
 #include "googleurl/src/gurl.h"
 #include "third_party/WebKit/public/platform/WebReferrerPolicy.h"
 #include "webkit/common/webkit_common_export.h"
 
 struct IDataObject;
 
 namespace WebKit {
 class WebDragData;
 }
@@ skipping 28 matching lines @@
   // a download.
   WebKit::WebReferrerPolicy referrer_policy;
 
   // User is dropping one or more files on the webview.
   std::vector<FileInfo> filenames;
 
   // Isolated filesystem ID for the files being dragged on the webview.
   base::string16 filesystem_id;
 
   // User is dragging plain text into the webview.
-  NullableString16 text;
+  base::NullableString16 text;
 
   // User is dragging text/html into the webview (e.g., out of Firefox).
   // |html_base_url| is the URL that the html fragment is taken from (used to
   // resolve relative links).  It's ok for |html_base_url| to be empty.
-  NullableString16 html;
+  base::NullableString16 html;
   GURL html_base_url;
 
   // User is dragging data from the webview (e.g., an image).
   base::string16 file_description_filename;
   std::string file_contents;
 
   std::map<base::string16, base::string16> custom_data;
 };
 
 #endif  // WEBKIT_COMMON_WEBDROPDATA_H_