Accessibility manager shouldn't try to access ash Shelf from login screen.

chrome/browser/chromeos/accessibility/chromevox_panel.h

 // Copyright 2015 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_CHROMEOS_ACCESSIBILITY_CHROMEVOX_PANEL_H_
 #define CHROME_BROWSER_CHROMEOS_ACCESSIBILITY_CHROMEVOX_PANEL_H_
 
 #include <stdint.h>
 
 #include "base/macros.h"
@@ skipping 13 matching lines @@
 class ChromeVoxPanel : public views::WidgetDelegate,
                        public gfx::DisplayObserver {
  public:
   explicit ChromeVoxPanel(content::BrowserContext* browser_context);
   ~ChromeVoxPanel() override;
 
   aura::Window* GetRootWindow();
 
   void Close();
   void DidFirstVisuallyNonEmptyPaint();
+  void UpdatePanelHeight();
   void EnterFullscreen();
   void ExitFullscreen();
   void DisableSpokenFeedback();
   void Focus();
 
   // WidgetDelegate overrides.
   const views::Widget* GetWidget() const override;
   views::Widget* GetWidget() override;
   void DeleteDelegate() override;
   views::View* GetContentsView() override;
 
   // DisplayObserver overrides;
   void OnDisplayAdded(const gfx::Display& new_display) override {}
   void OnDisplayRemoved(const gfx::Display& old_display) override {}
   void OnDisplayMetricsChanged(const gfx::Display& display,
                                uint32_t changed_metrics) override;
 
  private:
   void UpdateWidgetBounds();
 
   views::Widget* widget_;
   scoped_ptr<ChromeVoxPanelWebContentsObserver> web_contents_observer_;
   views::View* web_view_;
   bool fullscreen_;
 
   DISALLOW_COPY_AND_ASSIGN(ChromeVoxPanel);
 };
 
 #endif  // CHROME_BROWSER_CHROMEOS_ACCESSIBILITY_CHROMEVOX_PANEL_H_