Prevents crash when a menu gets closed during drag

ui/views/controls/menu/menu_host.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/controls/menu/menu_host.h"
 
 #include "base/auto_reset.h"
 #include "base/debug/trace_event.h"
 #include "ui/events/gestures/gesture_recognizer.h"
 #include "ui/gfx/path.h"
@@ skipping 74 matching lines @@
   ReleaseMenuHostCapture();
   Hide();
   ignore_capture_lost_ = false;
 }
 
 void MenuHost::DestroyMenuHost() {
   HideMenuHost();
   destroying_ = true;
   static_cast<MenuHostRootView*>(GetRootView())->ClearSubmenu();
   Close();
+  // Since |submenu_| is not a child view it is necessary to notify its
+  // observers so that they can clean up the focus and drag and drop state.
+  View::ViewHierarchyChangedDetails details(false, NULL, submenu_, NULL);
+  ViewHierarchyChanged(details);

[sky, 2014/03/27 21:40:43]

I think this is a deficiency in how focus is cleaning things up and you
shouldn't work around it like this.

[varkha, 2014/03/27 22:05:10]

In this case the menu does not have focus (the menu is dropped down by the drag
over it, not by a click) and the focus can be anywhere else - even in a
different instance. The crash happens in DropHelper::NotifyDragExit() because
the DropHelper::target_view_ (of the SubmenuView class) is still not NULL but
has been destroyed when the menu was closed and failed to notify the Widget.
Should we call NativeWidgetPrivate::ViewRemoved in some other code path?

[sky, 2014/03/27 23:31:28]

Isn't this happening because SubmenuView is client owned so that when the
RootView is deleted no notification is sent for the SubmenuView?

 }
 
 void MenuHost::SetMenuHostBounds(const gfx::Rect& bounds) {
   SetBounds(bounds);
 }
 
 void MenuHost::ReleaseMenuHostCapture() {
   if (native_widget_private()->HasCapture())
     native_widget_private()->ReleaseCapture();
 }
@@ skipping 29 matching lines @@
   if (destroying_)
     return;
 
   MenuController* menu_controller =
       submenu_->GetMenuItem()->GetMenuController();
   if (menu_controller && !menu_controller->drag_in_progress())
     menu_controller->CancelAll();
 }
 
 }  // namespace views