Add an identity (id) to system drag & drop.

webkit/glue/webdropdata.h

 // Copyright (c) 2006-2008 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_GLUE_WEBDROPDATA_H_
 #define WEBKIT_GLUE_WEBDROPDATA_H_
 
 #include <string>
 #include <vector>
 #include "googleurl/src/gurl.h"
 
 struct IDataObject;
 
 struct WebDropData {
-  // User is dropping a link on the webview.
+  // Construct with a given drag identity.  Note: identity is an int32 because
+  // it is passed over the renderer NPAPI interface to gears.
+  explicit WebDropData(int32 drag_identity) : identity(drag_identity) {}
+  int32 identity;
+
+  // For default constructions, use drag |identity| 0.
+  WebDropData() : identity(0) {}
+
+  // User is dragging a link into the webview.
   GURL url;
   std::wstring url_title;  // The title associated with |url|.
 
   // File extension for dragging images from a webview to the desktop.
   std::wstring file_extension;
 
   // User is dropping one or more files on the webview.
   std::vector<std::wstring> filenames;
 
   // User is dragging plain text into the webview.
@@ skipping 10 matching lines @@
   std::string file_contents;
 
   // Helper method for converting Window's specific IDataObject to a WebDropData
   // object.  TODO(tc): Move this to the browser side since it's Windows
   // specific and no longer used in webkit.
   static void PopulateWebDropData(IDataObject* data_object,
                                   WebDropData* drop_data);
 };
 
 #endif  // WEBKIT_GLUE_WEBDROPDATA_H_