Ensure Multi-finger tap generates both GestureScrollBegin and GestureScrollEnd.

ui/events/gestures/gesture_sequence.cc

Index: ui/events/gestures/gesture_sequence.cc
diff --git a/ui/events/gestures/gesture_sequence.cc b/ui/events/gestures/gesture_sequence.cc
index 5ee5d5e53fbe6204b204c0755773fd60bf4fbd1c..b9f7e6e97917962740cc89711528f2c81a08617d 100644
--- a/ui/events/gestures/gesture_sequence.cc
+++ b/ui/events/gestures/gesture_sequence.cc
@@ -633,7 +633,7 @@ GestureSequence::Gestures* GestureSequence::ProcessTouchEventForGesture(
     case GST_PENDING_TWO_FINGER_TAP_FIRST_RELEASED:
     case GST_PENDING_TWO_FINGER_TAP_SECOND_RELEASED:
       TwoFingerTouchReleased(event, point, gestures.get());
-      set_state(GS_SCROLL);
+      StartRailFreeScroll(point, gestures.get());
       break;
     case GST_PENDING_TWO_FINGER_TAP_FIRST_MOVED:
     case GST_PENDING_TWO_FINGER_TAP_SECOND_MOVED:
@@ -648,8 +648,7 @@ GestureSequence::Gestures* GestureSequence::ProcessTouchEventForGesture(
     case GST_PENDING_TWO_FINGER_TAP_SECOND_RELEASED_HANDLED:
     case GST_PENDING_TWO_FINGER_TAP_FIRST_CANCELLED:
     case GST_PENDING_TWO_FINGER_TAP_SECOND_CANCELLED:
-      scroll_type_ = ST_FREE;
-      set_state(GS_SCROLL);
+      StartRailFreeScroll(point, gestures.get());
       break;
     case GST_PENDING_TWO_FINGER_TAP_THIRD_PRESSED:
       set_state(GS_PENDING_PINCH);
@@ -661,18 +660,17 @@ GestureSequence::Gestures* GestureSequence::ProcessTouchEventForGesture(
     case GST_PENDING_TWO_FINGER_TAP_NO_PINCH_FIRST_RELEASED:
     case GST_PENDING_TWO_FINGER_TAP_NO_PINCH_SECOND_RELEASED:
       TwoFingerTouchReleased(event, point, gestures.get());
-      // We transit into GS_SCROLL even though the touch move can be
-      // consumed and no scroll should happen. crbug.com/240399.
-      set_state(GS_SCROLL);
+      // We transition into GS_SCROLL even though the touch move can be consumed
+      // and no scroll should happen. crbug.com/240399.
+      StartRailFreeScroll(point, gestures.get());
       break;
     case GST_PENDING_TWO_FINGER_TAP_NO_PINCH_FIRST_RELEASED_HANDLED:
     case GST_PENDING_TWO_FINGER_TAP_NO_PINCH_SECOND_RELEASED_HANDLED:
     case GST_PENDING_TWO_FINGER_TAP_NO_PINCH_FIRST_CANCELLED:
     case GST_PENDING_TWO_FINGER_TAP_NO_PINCH_SECOND_CANCELLED:
-      // We transit into GS_SCROLL even though the touch move can be
-      // consumed and no scroll should happen. crbug.com/240399.
-      scroll_type_ = ST_FREE;
-      set_state(GS_SCROLL);
+      // We transition into GS_SCROLL even though the touch move can be consumed
+      // and no scroll should happen. crbug.com/240399.
+      StartRailFreeScroll(point, gestures.get());
       break;
     case GST_PENDING_PINCH_FIRST_MOVED:
     case GST_PENDING_PINCH_SECOND_MOVED:
@@ -687,10 +685,9 @@ GestureSequence::Gestures* GestureSequence::ProcessTouchEventForGesture(
     case GST_PENDING_PINCH_SECOND_RELEASED:
     case GST_PENDING_PINCH_FIRST_CANCELLED:
     case GST_PENDING_PINCH_SECOND_CANCELLED:
-      // We transit into GS_SCROLL even though the touch move can be
-      // consumed and no scroll should happen. crbug.com/240399.
-      scroll_type_ = ST_FREE;
-      set_state(GS_SCROLL);
+      // We transition into GS_SCROLL even though the touch move can be consumed
+      // and no scroll should happen. crbug.com/240399.
+      StartRailFreeScroll(point, gestures.get());
       break;
     case GST_PENDING_PINCH_NO_PINCH_FIRST_MOVED:
     case GST_PENDING_PINCH_NO_PINCH_SECOND_MOVED:
@@ -700,10 +697,9 @@ GestureSequence::Gestures* GestureSequence::ProcessTouchEventForGesture(
     case GST_PENDING_PINCH_NO_PINCH_SECOND_RELEASED:
     case GST_PENDING_PINCH_NO_PINCH_FIRST_CANCELLED:
     case GST_PENDING_PINCH_NO_PINCH_SECOND_CANCELLED:
-      // We transit into GS_SCROLL even though the touch move can be
-      // consumed and no scroll should happen. crbug.com/240399.
-      scroll_type_ = ST_FREE;
-      set_state(GS_SCROLL);
+      // We transition into GS_SCROLL even though the touch move can be consumed
+      // and no scroll should happen. crbug.com/240399.
+      StartRailFreeScroll(point, gestures.get());
       break;
     case GST_PINCH_FIRST_MOVED_HANDLED:
     case GST_PINCH_SECOND_MOVED_HANDLED:
@@ -1479,4 +1475,11 @@ void GestureSequence::StopTimersIfRequired(const TouchEvent& event) {
   }
 }
 
+void GestureSequence::StartRailFreeScroll(const GesturePoint& point,
+                                          Gestures* gestures) {
+  AppendScrollGestureBegin(point, point.first_touch_position(), gestures);
+  scroll_type_ = ST_FREE;
+  set_state(GS_SCROLL);
+}
+
 }  // namespace ui