Add a11y on-screen keyboard to accessibility menu on system tray.

ash/default_accessibility_delegate.h

Index: ash/default_accessibility_delegate.h
diff --git a/ash/default_accessibility_delegate.h b/ash/default_accessibility_delegate.h
index ad0b6842534e8e7643010106c4cccea32423192e..62542186441cd243cd9d210557e177d5c3145090 100644
--- a/ash/default_accessibility_delegate.h
+++ b/ash/default_accessibility_delegate.h
@@ -29,6 +29,7 @@ class ASH_EXPORT DefaultAccessibilityDelegate : public AccessibilityDelegate {
   virtual bool IsLargeCursorEnabled() const OVERRIDE;
   virtual void SetAutoclickEnabled(bool enabled) OVERRIDE;
   virtual bool IsAutoclickEnabled() const OVERRIDE;
+  virtual void SetVirtualKeyboardEnabled(bool enabled) OVERRIDE;
   virtual bool IsVirtualKeyboardEnabled() const OVERRIDE;
   virtual bool ShouldShowAccessibilityMenu() const OVERRIDE;
   virtual void SilenceSpokenFeedback() const OVERRIDE;
@@ -47,6 +48,7 @@ class ASH_EXPORT DefaultAccessibilityDelegate : public AccessibilityDelegate {
   MagnifierType screen_magnifier_type_;
   bool large_cursor_enabled_;
   bool autoclick_enabled_;
+  bool virtual_keyboard_enabled_;
   AccessibilityAlert accessibility_alert_;
   DISALLOW_COPY_AND_ASSIGN(DefaultAccessibilityDelegate);
 };