Support 3f swipe for tab scrubbing

ui/base/events/event_utils.h

Index: ui/base/events/event_utils.h
diff --git a/ui/base/events/event_utils.h b/ui/base/events/event_utils.h
index 1e1240ea912337df026ab616f628079ce2baf74b..77e542f04922732094b4f532fb82b7cf6bd0f7c6 100644
--- a/ui/base/events/event_utils.h
+++ b/ui/base/events/event_utils.h
@@ -92,10 +92,11 @@ UI_EXPORT bool GetFlingData(const base::NativeEvent& native_event,
                             bool* is_cancel);
 
 // Returns whether this is a scroll event and optionally gets the amount to be
-// scrolled. |x_offset| and |y_offset| can be NULL.
+// scrolled. |x_offset|, |y_offset| and |finger_count| can be NULL.
 UI_EXPORT bool GetScrollOffsets(const base::NativeEvent& native_event,
                                 float* x_offset,
-                                float* y_offset);
+                                float* y_offset,
+                                int* finger_count);
 
 UI_EXPORT bool GetGestureTimes(const base::NativeEvent& native_event,
                                double* start_time,