Make shelf item can be dragged when context menu is opened.

ui/views/controls/menu/menu_host.h

 // 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.
 
 #ifndef UI_VIEWS_CONTROLS_MENU_MENU_HOST_H_
 #define UI_VIEWS_CONTROLS_MENU_MENU_HOST_H_
 
 #include <memory>
 
 #include "base/compiler_specific.h"
@@ skipping 28 matching lines @@
 class MenuHost : public Widget {
  public:
   explicit MenuHost(SubmenuView* submenu);
   ~MenuHost() override;
 
   // Initializes and shows the MenuHost.
   // WARNING: |parent| may be NULL.
   void InitMenuHost(Widget* parent,
                     const gfx::Rect& bounds,
                     View* contents_view,
-                    bool do_capture);
+                    bool do_capture,
+                    bool cancel_active_touches);
 
   // Returns true if the menu host is visible.
   bool IsMenuHostVisible();
 
   // Shows the menu host. If |do_capture| is true the menu host should do a
   // mouse grab.
-  void ShowMenuHost(bool do_capture);
+  void ShowMenuHost(bool do_capture, bool cancel_active_touches);
 
   // Hides the menu host.
   void HideMenuHost();
 
   // Destroys and deletes the menu host.
   void DestroyMenuHost();
 
   // Sets the bounds of the menu host.
   void SetMenuHostBounds(const gfx::Rect& bounds);
 
   // Releases a mouse grab installed by |ShowMenuHost|.
   void ReleaseMenuHostCapture();
 
+  void TransferEvents(Widget* source, Widget* target);
+
  private:
   friend class test::MenuControllerTest;
 
   // Overridden from Widget:
   internal::RootView* CreateRootView() override;
   void OnMouseCaptureLost() override;
   void OnNativeWidgetDestroyed() override;
   void OnOwnerClosing() override;
   void OnDragWillStart() override;
   void OnDragComplete() override;
 
   // The view we contain.
   SubmenuView* submenu_;
 
+  Widget* owner_ = NULL;
   // If true, DestroyMenuHost has been invoked.
   bool destroying_;
 
   // If true and capture is lost we don't notify the delegate.
   bool ignore_capture_lost_;
 
 #if !defined(OS_MACOSX)
   // Handles raw touch events at the moment.
   std::unique_ptr<internal::PreMenuEventDispatchHandler> pre_dispatch_handler_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(MenuHost);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_CONTROLS_MENU_MENU_HOST_H_