Prevent crash when desktop controller is NULL

ash/root_window_controller.cc

Index: ash/root_window_controller.cc
diff --git a/ash/root_window_controller.cc b/ash/root_window_controller.cc
index 3af8f489002c05f1b530354e6ab9b435037b7505..5fa1934d18fc2ce54b53b7df1c3748fafff22ac0 100644
--- a/ash/root_window_controller.cc
+++ b/ash/root_window_controller.cc
@@ -464,15 +464,20 @@ void RootWindowController::ShowContextMenu(
   if (!menu_model.get())
     return;
 
-  views::MenuRunner menu_runner(menu_model.get());
-  views::Widget* widget =
-      root_window_->GetProperty(kDesktopController)->widget();
+  internal::DesktopBackgroundWidgetController* background =
+      root_window_->GetProperty(kDesktopController);
+  // Background controller may not be set yet if user clicked on status are
+  // before initial animation completion. See crbug.com/222218
+  if (!background)
+    return;
 
-  if (menu_runner.RunMenuAt(
-          widget, NULL, gfx::Rect(location_in_screen, gfx::Size()),
+  views::MenuRunner menu_runner(menu_model.get());
+  if (menu_runner.RunMenuAt(background->widget(),
+          NULL, gfx::Rect(location_in_screen, gfx::Size()),
           views::MenuItemView::TOPLEFT, views::MenuRunner::CONTEXT_MENU) ==
-      views::MenuRunner::MENU_DELETED)
+      views::MenuRunner::MENU_DELETED) {
     return;
+  }
 
   Shell::GetInstance()->UpdateShelfVisibility();
 }