Potential fix for browser crash while ChromeVox is on.

chrome/browser/ui/aura/accessibility/automation_manager_aura.h

 // 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.
 
 #ifndef CHROME_BROWSER_UI_AURA_ACCESSIBILITY_AUTOMATION_MANAGER_AURA_H_
 #define CHROME_BROWSER_UI_AURA_ACCESSIBILITY_AUTOMATION_MANAGER_AURA_H_
 
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
 #include "chrome/browser/extensions/api/automation_internal/automation_action_adapter.h"
 #include "chrome/browser/ui/aura/accessibility/ax_tree_source_aura.h"
 #include "ui/accessibility/ax_tree_serializer.h"
+#include "ui/aura/window_observer.h"
 #include "ui/views/focus/widget_focus_manager.h"
 
 template <typename T>
 struct DefaultSingletonTraits;
 
 namespace content {
 class BrowserContext;
 }  // namespace content
 
 namespace views {
 class AXAuraObjWrapper;
 class View;
 }  // namespace views
 
 // Manages a tree of automation nodes.
 class AutomationManagerAura : public extensions::AutomationActionAdapter,
+                              public aura::WindowObserver,
                               public views::WidgetFocusChangeListener {
  public:
   // Get the single instance of this class.
   static AutomationManagerAura* GetInstance();
 
   // Enable automation support for views.
   void Enable(content::BrowserContext* context);
 
   // Disable automation support for views.
   void Disable();
@@ skipping 20 matching lines @@
 
   AutomationManagerAura();
 
   // Reset all state in this manager.
   void ResetSerializer();
 
   void SendEvent(content::BrowserContext* context,
                  views::AXAuraObjWrapper* aura_obj,
                  ui::AXEvent event_type);
 
+  // aura::WindowObserver:
+  void OnWindowDestroying(aura::Window* window) override;
+
   // views::WidgetFocusChangeListener:
   void OnNativeFocusChanged(aura::Window* focused_now) override;
 
   // Whether automation support for views is enabled.
   bool enabled_;
 
   // Holds the active views-based accessibility tree. A tree currently consists
   // of all views descendant to a |Widget| (see |AXTreeSourceViews|).
   // A tree becomes active when an event is fired on a descendant view.
   scoped_ptr<AXTreeSourceAura> current_tree_;
 
   // Serializes incremental updates on the currently active tree
   // |current_tree_|.
   scoped_ptr<ui::AXTreeSerializer<views::AXAuraObjWrapper*>>
       current_tree_serializer_;
 
   bool processing_events_;
 
   std::vector<std::pair<views::AXAuraObjWrapper*, ui::AXEvent>> pending_events_;
 
   aura::Window* focused_window_;
 
   DISALLOW_COPY_AND_ASSIGN(AutomationManagerAura);
 };
 
 #endif  // CHROME_BROWSER_UI_AURA_ACCESSIBILITY_AUTOMATION_MANAGER_AURA_H_