Prevent crash when desktop controller is NULL

ash/root_window_controller.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 "ash/root_window_controller.h"
 
 #include <vector>
 
 #include "ash/ash_constants.h"
 #include "ash/ash_switches.h"
@@ skipping 446 matching lines @@
 void RootWindowController::ShowContextMenu(
     const gfx::Point& location_in_screen) {
   aura::RootWindow* target = Shell::IsLauncherPerDisplayEnabled() ?
       root_window() : Shell::GetPrimaryRootWindow();
   DCHECK(Shell::GetInstance()->delegate());
   scoped_ptr<ui::MenuModel> menu_model(
       Shell::GetInstance()->delegate()->CreateContextMenu(target));
   if (!menu_model.get())
     return;
 
+  internal::DesktopBackgroundWidgetController* background =
+      root_window_->GetProperty(kDesktopController);
+  if (!background)

[oshima, 2013/04/04 13:44:51]

can you explain when this happens in the comment with a reference to the bug?

[Dmitry Polukhin, 2013/04/04 14:42:45]

Done.

+    return;
+
+  views::Widget* widget = background->widget();
+  if (!widget)
+    return;

[oshima, 2013/04/04 13:44:51]

can this happen?

[Dmitry Polukhin, 2013/04/04 14:42:45]

I haven't seen this - removed.

+
   views::MenuRunner menu_runner(menu_model.get());
-  views::Widget* widget =
-      root_window_->GetProperty(kDesktopController)->widget();
-
   if (menu_runner.RunMenuAt(
           widget, NULL, gfx::Rect(location_in_screen, gfx::Size()),
           views::MenuItemView::TOPLEFT, views::MenuRunner::CONTEXT_MENU) ==
       views::MenuRunner::MENU_DELETED)
     return;
 
   Shell::GetInstance()->UpdateShelfVisibility();
 }
 
 void RootWindowController::UpdateShelfVisibility() {
@@ skipping 164 matching lines @@
       "OverlayContainer",
       lock_screen_related_containers);
   SetUsesScreenCoordinates(overlay_container);
 
   CreateContainer(kShellWindowId_PowerButtonAnimationContainer,
                   "PowerButtonAnimationContainer", root_window) ;
 }
 
 }  // namespace internal
 }  // namespace ash