Re-land: Toggle spoken feedback if two fingers are held down.

ash/common/accessibility_delegate.h

Index: ash/common/accessibility_delegate.h
diff --git a/ash/common/accessibility_delegate.h b/ash/common/accessibility_delegate.h
index 36ea7080e177241a45ae30b532784bf382bd105a..25c0665ca1129fe14ba03febec17b26795aee4fa 100644
--- a/ash/common/accessibility_delegate.h
+++ b/ash/common/accessibility_delegate.h
@@ -121,6 +121,13 @@ class ASH_EXPORT AccessibilityDelegate {
   // Gets the last accessibility alert that was triggered.
   virtual AccessibilityAlert GetLastAccessibilityAlert() = 0;
 
+  // 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.