Fix deadlock between UI thread and drag and drop thread on Windows.

content/browser/web_contents/web_drag_source_win.cc

 // 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.
 
 #include "content/browser/web_contents/web_drag_source_win.h"
 
 #include "base/bind.h"
 #include "content/browser/renderer_host/render_view_host_impl.h"
 #include "content/browser/web_contents/web_drag_utils_win.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/notification_source.h"
 #include "content/public/browser/notification_types.h"
 #include "content/public/browser/web_contents.h"
+#include "ui/base/dragdrop/os_exchange_data.h"
 
 using WebKit::WebDragOperationNone;
 
 namespace content {
 namespace {
 
 static void GetCursorPositions(gfx::NativeWindow wnd, gfx::Point* client,
                                gfx::Point* screen) {
   POINT cursor_pos;
   GetCursorPos(&cursor_pos);
   screen->SetPoint(cursor_pos.x, cursor_pos.y);
   ScreenToClient(wnd, &cursor_pos);
   client->SetPoint(cursor_pos.x, cursor_pos.y);
 }
 
 }  // namespace
 
 ///////////////////////////////////////////////////////////////////////////////
 // WebDragSource, public:
 
 WebDragSource::WebDragSource(gfx::NativeWindow source_wnd,
                              WebContents* web_contents)
     : ui::DragSourceWin(),
       source_wnd_(source_wnd),
       render_view_host_(web_contents->GetRenderViewHost()),
-      effect_(DROPEFFECT_NONE) {
+      effect_(DROPEFFECT_NONE),
+      data_(NULL) {
   registrar_.Add(this, NOTIFICATION_WEB_CONTENTS_SWAPPED,
                  Source<WebContents>(web_contents));
   registrar_.Add(this, NOTIFICATION_WEB_CONTENTS_DISCONNECTED,
                  Source<WebContents>(web_contents));
 }
 
 WebDragSource::~WebDragSource() {
 }
 
 void WebDragSource::OnDragSourceCancel() {
@@ skipping 10 matching lines @@
 
   gfx::Point client;
   gfx::Point screen;
   GetCursorPositions(source_wnd_, &client, &screen);
   render_view_host_->DragSourceEndedAt(client.x(), client.y(),
                                        screen.x(), screen.y(),
                                        WebDragOperationNone);
 }
 
 void WebDragSource::OnDragSourceDrop() {
+  DCHECK(data_);
+  data_->SetInDragLoop(false);
   // On Windows, we check for drag end in IDropSource::QueryContinueDrag which
   // happens before IDropTarget::Drop is called. HTML5 requires the "dragend"
   // event to happen after the "drop" event. Since  Windows calls these two
   // directly after each other we can just post a task to handle the
   // OnDragSourceDrop after the current task.
   BrowserThread::PostTask(
       BrowserThread::UI, FROM_HERE,
       base::Bind(&WebDragSource::DelayedOnDragSourceDrop, this));
 }
 
@@ skipping 38 matching lines @@
     render_view_host_ = NULL;
   } else if (type == NOTIFICATION_WEB_CONTENTS_DISCONNECTED) {
     // This could be possible when we close the tab and the source is still
     // being used in DoDragDrop at the time that the virtual file is being
     // downloaded.
     render_view_host_ = NULL;
   }
 }
 
 }  // namespace content