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

chrome/browser/tab_contents/web_drop_target.cc

 // 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.
 
 #include <windows.h>
 #include <shlobj.h>
 
 #include "chrome/browser/tab_contents/web_drop_target.h"
 
 #include "base/clipboard_util.h"
@@ skipping 82 matching lines @@
   current_rvh_ = web_contents_->render_view_host();
 
   // Don't pass messages to the renderer if an interstitial page is showing
   // because we don't want the interstitial page to navigate.  Instead,
   // pass the messages on to a separate interstitial DropTarget handler.
   if (web_contents_->showing_interstitial_page())
     return interstitial_drop_target_->OnDragEnter(data_object, effect);
 
   // TODO(tc): PopulateWebDropData can be slow depending on what is in the
   // IDataObject.  Maybe we can do this in a background thread.
-  WebDropData drop_data;
+  WebDropData drop_data(GetDragIdentity());
   WebDropData::PopulateWebDropData(data_object, &drop_data);
 
   if (drop_data.url.is_empty())
     OSExchangeData::GetPlainTextURL(data_object, &drop_data.url);
 
   is_drop_target_ = true;
 
   POINT client_pt = cursor_position;
   ScreenToClient(GetHWND(), &client_pt);
   web_contents_->render_view_host()->DragTargetDragEnter(drop_data,
@@ skipping 15 matching lines @@
 
   if (web_contents_->showing_interstitial_page())
     return interstitial_drop_target_->OnDragOver(data_object, effect);
 
   POINT client_pt = cursor_position;
   ScreenToClient(GetHWND(), &client_pt);
   web_contents_->render_view_host()->DragTargetDragOver(
       gfx::Point(client_pt.x, client_pt.y),
       gfx::Point(cursor_position.x, cursor_position.y));
 
+  // Again we don't wait on the renderer to respond, but this can lead to
+  // a race condition.  If the renderer does not want the drop data, then
+  // we won't know until the response from the renderer arrives.  So if a
+  // drop happens before the response arrives, we drop on a renderer that
+  // doesn't want the data.  TODO(noel): fix this.
+
   if (!is_drop_target_)
     return DROPEFFECT_NONE;
 
   return GetPreferredDropEffect(effect);
 }
 
 void WebDropTarget::OnDragLeave(IDataObject* data_object) {
   DCHECK(current_rvh_);
   if (current_rvh_ != web_contents_->render_view_host())
     return;
@@ skipping 24 matching lines @@
   web_contents_->render_view_host()->DragTargetDrop(
       gfx::Point(client_pt.x, client_pt.y),
       gfx::Point(cursor_position.x, cursor_position.y));
 
   current_rvh_ = NULL;
 
   // We lie and always claim that the drop operation didn't happen because we
   // don't want to wait for the renderer to respond.
   return DROPEFFECT_NONE;
 }