Reland: Fix crash when the source browser window is deleted during a drag

ui/views/widget/desktop_aura/desktop_drag_drop_client_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 "ui/views/widget/desktop_aura/desktop_drag_drop_client_win.h"
 
 #include "base/tracked_objects.h"
 #include "ui/base/dragdrop/drag_drop_types.h"
 #include "ui/base/dragdrop/drag_source_win.h"
 #include "ui/base/dragdrop/drop_target_event.h"
 #include "ui/base/dragdrop/os_exchange_data_provider_win.h"
 #include "ui/views/widget/desktop_aura/desktop_drop_target_win.h"
 #include "ui/views/widget/desktop_aura/desktop_window_tree_host_win.h"
 
 namespace views {
 
 DesktopDragDropClientWin::DesktopDragDropClientWin(
     aura::Window* root_window,
     HWND window)
     : drag_drop_in_progress_(false),
-      drag_operation_(0) {
+      drag_operation_(0),
+      weak_factory_(this) {
   drop_target_ = new DesktopDropTargetWin(root_window, window);
 }
 
 DesktopDragDropClientWin::~DesktopDragDropClientWin() {
+  if (drag_drop_in_progress_)
+    DragCancel();
 }
 
 int DesktopDragDropClientWin::StartDragAndDrop(
     const ui::OSExchangeData& data,
     aura::Window* root_window,
     aura::Window* source_window,
     const gfx::Point& root_location,
     int operation,
     ui::DragDropTypes::DragEventSource source) {
   drag_drop_in_progress_ = true;
   drag_operation_ = operation;
 
+  base::WeakPtr<DesktopDragDropClientWin> alive(weak_factory_.GetWeakPtr());
+
   drag_source_ = new ui::DragSourceWin;
+  scoped_refptr<ui::DragSourceWin> drag_source_copy = drag_source_;
+
   DWORD effect;
 
   // Use task stopwatch to exclude the drag-drop time current task, if any.
   tracked_objects::TaskStopwatch stopwatch;
   stopwatch.Start();
   HRESULT result = DoDragDrop(
       ui::OSExchangeDataProviderWin::GetIDataObject(data), drag_source_.get(),
       ui::DragDropTypes::DragOperationToDropEffect(operation), &effect);
   stopwatch.Stop();
 
-  drag_drop_in_progress_ = false;
+  if (alive)
+    drag_drop_in_progress_ = false;
 
   if (result != DRAGDROP_S_DROP)
     effect = DROPEFFECT_NONE;
 
   return ui::DragDropTypes::DropEffectToDragOperation(effect);
 }
 
 void DesktopDragDropClientWin::DragUpdate(aura::Window* target,
                                           const ui::LocatedEvent& event) {
 }
@@ skipping 12 matching lines @@
 }
 
 void DesktopDragDropClientWin::OnNativeWidgetDestroying(HWND window) {
   if (drop_target_.get()) {
     RevokeDragDrop(window);
     drop_target_ = NULL;
   }
 }
 
 }  // namespace views