Check that a view exists before sending an accessibility event.

ui/views/accessibility/ax_window_obj_wrapper.cc

 // Copyright 2014 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/accessibility/ax_window_obj_wrapper.h"
 
 #include <stddef.h>
 
 #include "base/strings/utf_string_conversions.h"
 #include "ui/accessibility/ax_node_data.h"
@@ skipping 69 matching lines @@
     const HierarchyChangeParams& params) {
   if (params.phase == WindowObserver::HierarchyChangeParams::HIERARCHY_CHANGED)
     AXAuraObjCache::GetInstance()->Remove(params.target, params.old_parent);
 }
 
 void AXWindowObjWrapper::OnWindowBoundsChanged(aura::Window* window,
                                                const gfx::Rect& old_bounds,
                                                const gfx::Rect& new_bounds) {
   Widget* widget = Widget::GetWidgetForNativeView(window);
   if (widget) {
-    widget->GetRootView()->NotifyAccessibilityEvent(
-        ui::AX_EVENT_LOCATION_CHANGED, true);
+    views::View* view = widget->GetRootView();
+    if (view) {
+      view->NotifyAccessibilityEvent(ui::AX_EVENT_LOCATION_CHANGED, true);
+    }
   }
 }
 
 }  // namespace views