Generate tap gesture with tap_count = 3 for triple-tap

ash/touch/touch_uma.cc

Index: ash/touch/touch_uma.cc
diff --git a/ash/touch/touch_uma.cc b/ash/touch/touch_uma.cc
index 8279bf65ed08f19379fd3a002e317607d3e1e253..ed234e0c2d776c24447acfb35d6239d7d5be2159 100644
--- a/ash/touch/touch_uma.cc
+++ b/ash/touch/touch_uma.cc
@@ -57,6 +57,7 @@ enum UMAEventType {
   UMA_ET_GESTURE_BEGIN,
   UMA_ET_GESTURE_END,
   UMA_ET_GESTURE_DOUBLE_TAP,
+  UMA_ET_GESTURE_TRIPLE_TAP,
   UMA_ET_GESTURE_TWO_FINGER_TAP,
   UMA_ET_GESTURE_PINCH_BEGIN,
   UMA_ET_GESTURE_PINCH_END,
@@ -203,6 +204,8 @@ UMAEventType UMAEventTypeFromEvent(const ui::Event& event) {
         return UMA_ET_GESTURE_TAP;
       else if (tap_count == 2)
         return UMA_ET_GESTURE_DOUBLE_TAP;
+      else if (tap_count == 3)
+        return UMA_ET_GESTURE_TRIPLE_TAP;
       NOTREACHED() << "Received tap with tapcount " << tap_count;
       return UMA_ET_UNKNOWN;
     }