Ensure Multi-finger tap generates both GestureScrollBegin and GestureScrollEnd.

ui/events/gestures/gesture_sequence.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/events/gestures/gesture_sequence.h"
 
 #include <stdlib.h>
 #include <cmath>
 #include <limits>
 
@@ skipping 615 matching lines @@
     case GST_SYNTHETIC_CLICK_ABORTED_SECOND_PRESSED:
       TwoFingerTapOrPinch(event, point, gestures.get());
       break;
     case GST_SCROLL_SECOND_PRESSED:
       PinchStart(event, point, gestures.get());
       set_state(GS_PINCH);
       break;
     case GST_PENDING_TWO_FINGER_TAP_FIRST_RELEASED:
     case GST_PENDING_TWO_FINGER_TAP_SECOND_RELEASED:
       TwoFingerTouchReleased(event, point, gestures.get());
+      AppendScrollGestureBegin(
+          point, point.first_touch_position(), gestures.get());
+      scroll_type_ = ST_FREE;
       set_state(GS_SCROLL);

[sadrul, 2014/03/10 03:54:52]

It may make sense to have a 'TransitionToScrollState()' for these 4 lines.

[tdresser, 2014/03/10 12:36:39]

Done. Named "StartRailFreeScroll," to indicate that it doesn't merely perform a
state change.

       break;
     case GST_PENDING_TWO_FINGER_TAP_FIRST_MOVED:
     case GST_PENDING_TWO_FINGER_TAP_SECOND_MOVED:
       if (TwoFingerTouchMove(event, point, gestures.get()))
         set_state(GS_PINCH);
       break;
     case GST_PENDING_TWO_FINGER_TAP_FIRST_MOVED_HANDLED:
     case GST_PENDING_TWO_FINGER_TAP_SECOND_MOVED_HANDLED:
       set_state(GS_PENDING_TWO_FINGER_TAP_NO_PINCH);
       break;
     case GST_PENDING_TWO_FINGER_TAP_FIRST_RELEASED_HANDLED:
     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:
+      AppendScrollGestureBegin(
+          point, point.first_touch_position(), gestures.get());
       scroll_type_ = ST_FREE;
       set_state(GS_SCROLL);
       break;
     case GST_PENDING_TWO_FINGER_TAP_THIRD_PRESSED:
       set_state(GS_PENDING_PINCH);
       break;
     case GST_PENDING_TWO_FINGER_TAP_NO_PINCH_FIRST_MOVED:
     case GST_PENDING_TWO_FINGER_TAP_NO_PINCH_SECOND_MOVED:
       // No pinch allowed, so nothing happens.
       break;
     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.
+      // We transition into GS_SCROLL even though the touch move can be consumed
+      // and no scroll should happen. crbug.com/240399.
+      AppendScrollGestureBegin(
+          point, point.first_touch_position(), gestures.get());
       set_state(GS_SCROLL);
       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.
+      // We transition into GS_SCROLL even though the touch move can be consumed
+      // and no scroll should happen. crbug.com/240399.
+      AppendScrollGestureBegin(
+          point, point.first_touch_position(), gestures.get());
       scroll_type_ = ST_FREE;
       set_state(GS_SCROLL);
       break;
     case GST_PENDING_PINCH_FIRST_MOVED:
     case GST_PENDING_PINCH_SECOND_MOVED:
       if (TwoFingerTouchMove(event, point, gestures.get()))
         set_state(GS_PINCH);
       break;
     case GST_PENDING_PINCH_FIRST_MOVED_HANDLED:
     case GST_PENDING_PINCH_SECOND_MOVED_HANDLED:
       set_state(GS_PENDING_PINCH_NO_PINCH);
       break;
     case GST_PENDING_PINCH_FIRST_RELEASED:
     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.
+      // We transition into GS_SCROLL even though the touch move can be consumed
+      // and no scroll should happen. crbug.com/240399.
+      AppendScrollGestureBegin(
+          point, point.first_touch_position(), gestures.get());
       scroll_type_ = ST_FREE;
       set_state(GS_SCROLL);
       break;
     case GST_PENDING_PINCH_NO_PINCH_FIRST_MOVED:
     case GST_PENDING_PINCH_NO_PINCH_SECOND_MOVED:
       // No pinch allowed, so nothing happens.
       break;
     case GST_PENDING_PINCH_NO_PINCH_FIRST_RELEASED:
     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.
+      // We transition into GS_SCROLL even though the touch move can be consumed
+      // and no scroll should happen. crbug.com/240399.
+      AppendScrollGestureBegin(
+          point, point.first_touch_position(), gestures.get());
       scroll_type_ = ST_FREE;
       set_state(GS_SCROLL);
       break;
     case GST_PINCH_FIRST_MOVED_HANDLED:
     case GST_PINCH_SECOND_MOVED_HANDLED:
     case GST_PINCH_THIRD_MOVED_HANDLED:
     case GST_PINCH_FOURTH_MOVED_HANDLED:
     case GST_PINCH_FIFTH_MOVED_HANDLED:
       break;
     case GST_PINCH_FIRST_MOVED:
@@ skipping 758 matching lines @@
 
   // Since a timer is running, there should be a non-NULL point.
   const GesturePoint* point = GetPointByPointId(0);
   if (!point->IsInsideTouchSlopRegion(event)) {
     GetLongPressTimer()->Stop();
     GetShowPressTimer()->Stop();
   }
 }
 
 }  // namespace ui