Fire accessibilityPrivate events on two-finger hold gesture.

ash/default_accessibility_delegate.cc

Index: ash/default_accessibility_delegate.cc
diff --git a/ash/default_accessibility_delegate.cc b/ash/default_accessibility_delegate.cc
index e2fd90a106504cabb4d0b7d3a0b63844f515db70..5770918f75df573a5b903ee22e46e621a9b7f2df 100644
--- a/ash/default_accessibility_delegate.cc
+++ b/ash/default_accessibility_delegate.cc
@@ -162,6 +162,10 @@ AccessibilityAlert DefaultAccessibilityDelegate::GetLastAccessibilityAlert() {
   return accessibility_alert_;
 }
 
+void DefaultAccessibilityDelegate::OnTwoFingerTouchStart() {}
+
+void DefaultAccessibilityDelegate::OnTwoFingerTouchStop() {}
+
 bool DefaultAccessibilityDelegate::ShouldToggleSpokenFeedbackViaTouch() {
   return false;
 }