Support dragging a virtual file out of the browser.

chrome/browser/tab_contents/web_drag_source_win.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 "chrome/browser/tab_contents/web_drag_source_win.h"
 
+#include "base/task.h"
+#include "chrome/browser/chrome_thread.h"
 #include "chrome/browser/renderer_host/render_view_host.h"
 #include "chrome/browser/tab_contents/tab_contents.h"
 #include "chrome/common/notification_type.h"
 #include "chrome/common/notification_service.h"
 
 using WebKit::WebDragOperationNone;
 using WebKit::WebDragOperationCopy;
 
 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,
                              TabContents* tab_contents)
     : BaseDragSource(),
       source_wnd_(source_wnd),
       render_view_host_(tab_contents->render_view_host()) {
   registrar_.Add(this, NotificationType::TAB_CONTENTS_SWAPPED,
                  Source<TabContents>(tab_contents));
   registrar_.Add(this, NotificationType::TAB_CONTENTS_DISCONNECTED,
                  Source<TabContents>(tab_contents));
 }
 
 void WebDragSource::OnDragSourceCancel() {
+  // Delegate to the UI thread if we do drag-and-drop in the background thread.
+  if (!ChromeThread::CurrentlyOn(ChromeThread::UI)) {
+    ChromeThread::PostTask(
+        ChromeThread::UI, FROM_HERE,
+        NewRunnableMethod(this, &WebDragSource::OnDragSourceCancel));
+    return;
+  }
+
   if (!render_view_host_)
     return;
 
   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() {
+  // Delegate to the UI thread if we do drag-and-drop in the background thread.
+  if (!ChromeThread::CurrentlyOn(ChromeThread::UI)) {
+    ChromeThread::PostTask(
+        ChromeThread::UI, FROM_HERE,
+        NewRunnableMethod(this, &WebDragSource::OnDragSourceDrop));
+    return;
+  }
+
   if (!render_view_host_)
     return;
 
   gfx::Point client;
   gfx::Point screen;
   GetCursorPositions(source_wnd_, &client, &screen);
   render_view_host_->DragSourceEndedAt(client.x(), client.y(),
                                        screen.x(), screen.y(),
                                        WebDragOperationCopy);
   // TODO(jpa): This needs to be fixed to send the actual drag operation.
 }
 
 void WebDragSource::OnDragSourceMove() {
+  // Delegate to the UI thread if we do drag-and-drop in the background thread.
+  if (!ChromeThread::CurrentlyOn(ChromeThread::UI)) {
+    ChromeThread::PostTask(
+        ChromeThread::UI, FROM_HERE,
+        NewRunnableMethod(this, &WebDragSource::OnDragSourceMove));
+    return;
+  }
+
   if (!render_view_host_)
     return;
 
   gfx::Point client;
   gfx::Point screen;
   GetCursorPositions(source_wnd_, &client, &screen);
   render_view_host_->DragSourceMovedTo(client.x(), client.y(),
                                        screen.x(), screen.y());
 }
 
 void WebDragSource::Observe(NotificationType type,
     const NotificationSource& source, const NotificationDetails& details) {
   if (NotificationType::TAB_CONTENTS_SWAPPED == type) {
     // When the tab contents get swapped, our render view host goes away.
     // That's OK, we can continue the drag, we just can't send messages back to
     // our drag source.
     render_view_host_ = NULL;
   } else if (NotificationType::TAB_CONTENTS_DISCONNECTED == type) {
-    NOTREACHED();
+    // 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;
   }
 }