Add GestureTapCancel gesture type

ui/base/gestures/gesture_sequence.cc

Index: ui/base/gestures/gesture_sequence.cc
diff --git a/ui/base/gestures/gesture_sequence.cc b/ui/base/gestures/gesture_sequence.cc
index d668a1e11e6137b473fbe62185806841e5b94e56..bf62f3646099e5f9deac25b71ea9689da35b1b70 100644
--- a/ui/base/gestures/gesture_sequence.cc
+++ b/ui/base/gestures/gesture_sequence.cc
@@ -368,11 +368,14 @@ GestureSequence::Gestures* GestureSequence::ProcessTouchEventForGesture(
     case GST_PENDING_SYNTHETIC_CLICK_FIRST_RELEASED:
       if (Click(event, point, gestures.get()))
         point.UpdateForTap();
+      else
+        AppendTapCancelGestureEvent(point, gestures.get());
       set_state(GS_NO_GESTURE);
       break;
     case GST_PENDING_SYNTHETIC_CLICK_FIRST_MOVED:
     case GST_PENDING_SYNTHETIC_CLICK_FIRST_STATIONARY:
       if (ScrollStart(event, point, gestures.get())) {
+        AppendTapCancelGestureEvent(point, gestures.get());

[sadrul, 2012/09/09 18:33:02]

This will add TAP_CANCEL after SCROLL_START. I think TAP_CANCEL should be before
SCROLL_START (and similarly, before PINCH_START). So AppendTapCancelGestureEvent
should be in ScrollStart, PinchStart (when state_ == PENDING_TAP), and
TwoFingerTouchDown (when state_ == PENDING_TAP)

[Rick Byers, 2012/09/10 00:56:26]

Yep, you're right - thanks.  I don't think it makes much difference in practice
which order they occur in, but I agree the order should be reversed.  I'll do
that.  

Since I was trying to make it clear that we send TapCancel (or Tap) on every
outgoing edge from the 'pending' state I wanted the sending of the event to be
next to the set_state calls (eg. it's not necessarily they case that we'll
always want to send this on every ScrollStart - in fact it gets more complicated
in this way in my fix for bug 146397), I'll come up with something.

BTW, this is something I don't like about our existing gesture recognizer unit
test infrastructure - it's too loose on what it validates (eg. makes it hard to
validate the order of events like this).  Tim's reworked log-based
infrastructure (that got reverted) was much better if I recall.  I'll see if
there's a small change I can make to validate this in the current infrastructure
without doing a major overhaul here.

         set_state(GS_SCROLL);
         if (ScrollUpdate(event, point, gestures.get()))
           point.UpdateForScroll();
@@ -380,6 +383,7 @@ GestureSequence::Gestures* GestureSequence::ProcessTouchEventForGesture(
       break;
     case GST_PENDING_SYNTHETIC_CLICK_FIRST_RELEASED_HANDLED:
     case GST_PENDING_SYNTHETIC_CLICK_FIRST_CANCELLED:
+      AppendTapCancelGestureEvent(point, gestures.get());
       set_state(GS_NO_GESTURE);
       break;
     case GST_SCROLL_FIRST_MOVED:
@@ -394,8 +398,10 @@ GestureSequence::Gestures* GestureSequence::ProcessTouchEventForGesture(
       ScrollEnd(event, point, gestures.get());
       set_state(GS_NO_GESTURE);
       break;
-    case GST_SCROLL_SECOND_PRESSED:
     case GST_PENDING_SYNTHETIC_CLICK_SECOND_PRESSED:
+      AppendTapCancelGestureEvent(point, gestures.get());
+      // fall through
+    case GST_SCROLL_SECOND_PRESSED:
       if (IsSecondTouchDownCloseEnoughForTwoFingerTap()) {
         TwoFingerTouchDown(event, point, gestures.get());
         set_state(GS_PENDING_TWO_FINGER_TAP);
@@ -597,6 +603,16 @@ void GestureSequence::AppendTapDownGestureEvent(const GesturePoint& point,
       1 << point.touch_id()));
 }
 
+void GestureSequence::AppendTapCancelGestureEvent(const GesturePoint& point,
+                                            Gestures* gestures) {
+    gestures->push_back(CreateGestureEvent(
+      GestureEventDetails(ui::ET_GESTURE_TAP_CANCEL, 0, 0),
+      point.first_touch_position(),
+      flags_,
+      base::Time::FromDoubleT(point.last_touch_time()),
+      1 << point.touch_id()));
+}
+
 void GestureSequence::AppendBeginGestureEvent(const GesturePoint& point,
                                               Gestures* gestures) {
   gestures->push_back(CreateGestureEvent(