Send screen on and off state as a11y alert

ash/common/accessibility_types.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 ASH_COMMON_ACCESSIBILITY_TYPES_H_
 #define ASH_COMMON_ACCESSIBILITY_TYPES_H_
 
 namespace ash {
 
 enum AccessibilityNotificationVisibility {
   A11Y_NOTIFICATION_NONE,
   A11Y_NOTIFICATION_SHOW,
 };
 
 enum AccessibilityAlert {
   A11Y_ALERT_NONE,
   A11Y_ALERT_CAPS_ON,
   A11Y_ALERT_CAPS_OFF,
+  A11Y_ALERT_SCREEN_ON,
+  A11Y_ALERT_SCREEN_OFF,
   A11Y_ALERT_WINDOW_NEEDED,
   A11Y_ALERT_WINDOW_OVERVIEW_MODE_ENTERED
 };
 
 // Note: Do not change these values; UMA and prefs depend on them.
 enum MagnifierType {
   MAGNIFIER_FULL = 1,
   MAGNIFIER_PARTIAL = 2,
 };
 
 const int kMaxMagnifierType = 2;
 
 const MagnifierType kDefaultMagnifierType = MAGNIFIER_FULL;
 
 // Factor of magnification scale. For example, when this value is 1.189, scale
 // value will be changed x1.000, x1.189, x1.414, x1.681, x2.000, ...
 // Note: this value is 2.0 ^ (1 / 4).
 const float kMagnificationScaleFactor = 1.18920712f;
 
 }  // namespace ash
 
 #endif  // ASH_COMMON_ACCESSIBILITY_TYPES_H_