Fire accessibilityPrivate events on two-finger hold gesture.

ash/accessibility_delegate.h

 // Copyright 2013 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_ACCESSIBILITY_DELEGATE_H_
 #define ASH_ACCESSIBILITY_DELEGATE_H_
 
 #include "ash/accessibility_types.h"
 #include "ash/ash_export.h"
 #include "base/time/time.h"
@@ skipping 115 matching lines @@
   // Gets a saved value of the zoom scale of full screen magnifier. If a value
   // is not saved, return a negative value.
   virtual double GetSavedScreenMagnifierScale() = 0;
 
   // Triggers an accessibility alert to give the user feedback.
   virtual void TriggerAccessibilityAlert(AccessibilityAlert alert) = 0;
 
   // Gets the last accessibility alert that was triggered.
   virtual AccessibilityAlert GetLastAccessibilityAlert() = 0;
 
+  // Called when we first detect two fingers are held down, which can be
+  // used to toggle spoken feedback on some touch-only devices.
+  virtual void OnTwoFingerTouchStart() {}
+
+  // Called when the user is no longer holding down two fingers (including
+  // releasing one, holding down three, or moving them).
+  virtual void OnTwoFingerTouchStop() {}
+
   // Whether or not to enable toggling spoken feedback via holding down
   // two fingers on the screen.
   virtual bool ShouldToggleSpokenFeedbackViaTouch() = 0;
 
   // Play tick sound indicating spoken feedback will be toggled after countdown.
   virtual void PlaySpokenFeedbackToggleCountdown(int tick_count) = 0;
 
   // Plays an earcon. Earcons are brief and distinctive sounds that indicate
   // when their mapped event has occurred. The sound key enums can be found in
   // chromeos/audio/chromeos_sounds.h.
   virtual void PlayEarcon(int sound_key) = 0;
 
   // Initiates play of shutdown sound and returns it's duration.
   virtual base::TimeDelta PlayShutdownSound() const = 0;
 
   // Forward an accessibility gesture from the touch exploration controller to
   // ChromeVox.
   virtual void HandleAccessibilityGesture(ui::AXGesture gesture) = 0;
 };
 
 }  // namespace ash
 
 #endif  // ASH_ACCESSIBILITY_DELEGATE_H_