Re-enable Eager Gesture Recognition on Aura

ui/events/gesture_detection/touch_disposition_gesture_filter.cc

Index: ui/events/gesture_detection/touch_disposition_gesture_filter.cc
diff --git a/ui/events/gesture_detection/touch_disposition_gesture_filter.cc b/ui/events/gesture_detection/touch_disposition_gesture_filter.cc
index 564d014a4c5f94c28a7bd9a72be4ec1c8c84d594..01b239ab8de0aa0334160d5cea9fb15011db71f2 100644
--- a/ui/events/gesture_detection/touch_disposition_gesture_filter.cc
+++ b/ui/events/gesture_detection/touch_disposition_gesture_filter.cc
@@ -170,7 +170,8 @@ TouchDispositionGestureFilter::OnGesturePacket(
   return SUCCESS;
 }
 
-void TouchDispositionGestureFilter::OnTouchEventAck(bool event_consumed) {
+void TouchDispositionGestureFilter::OnTouchEventAckForQueueFront(
+    bool event_consumed) {
   // Spurious touch acks from the renderer should not trigger a crash.
   if (IsEmpty() || (Head().empty() && sequences_.size() == 1))
     return;
@@ -178,12 +179,29 @@ void TouchDispositionGestureFilter::OnTouchEventAck(bool event_consumed) {
   if (Head().empty())
     PopGestureSequence();
 
-  GestureSequence& sequence = Head();
+  Head().front().ack(event_consumed);
+  SendAckedEvents();
+}
+
+void TouchDispositionGestureFilter::OnTouchEventAckForQueueBack(
+    bool event_consumed) {
+  // Spurious touch acks from the renderer should not trigger a crash.
+  if(IsEmpty() || Tail().empty())

[jdduke (slow), 2014/11/26 16:07:09]

Hmm, should an ack from the renderer ever hit the queue back? I kind of liked
the DCHECKs you had here.

[tdresser, 2014/11/27 18:26:25]

Done.

+    return;
+  Tail().back().ack(event_consumed);
+  SendAckedEvents();

[jdduke (slow), 2014/11/26 16:07:09]

Hmm, I'm not sure about this. Don't we only want to try sending if there's only
one event in the entire queue?

[tdresser, 2014/11/27 18:26:24]

I haven't come up with a case where having that guard here is any different from
just blocking on events closer to the head of the queue.

Do you think special casing that here is worth it?
-
On second though, it would let us assert that at least one packet was
dispatched, which is a nice property. Done.

+}
+
+void TouchDispositionGestureFilter::SendAckedEvents() {

[jdduke (slow), 2014/11/26 16:07:09]

Nice, the recursion avoidance may have been premature on my part but this looks
good.

[tdresser, 2014/11/27 18:26:25]

I think its a fair bit clearer this way, yeah.

+  // Dispatch all packets corresponding to ack'ed touches, as well as
+  // any pending timeout-based packets.
+  while (true) {

[jdduke (slow), 2014/11/26 16:07:09]

Would it make sense to push the if condition below into the while condition?

[tdresser, 2014/11/27 18:26:24]

Yuck. Fixed.

+    if (IsEmpty() || (Head().empty() && sequences_.size() == 1))
+      break;
+    if (Head().empty())
+      PopGestureSequence();
+    GestureSequence& sequence = Head();
 
-  // Dispatch the packet corresponding to the ack'ed touch, as well as any
-  // additional timeout-based packets queued before the ack was received.
-  bool touch_packet_for_current_ack_handled = false;
-  while (!sequence.empty()) {
     DCHECK_NE(sequence.front().gesture_source(),
               GestureEventDataPacket::UNDEFINED);
     DCHECK_NE(sequence.front().gesture_source(),
@@ -191,12 +209,15 @@ void TouchDispositionGestureFilter::OnTouchEventAck(bool event_consumed) {
 
     GestureEventDataPacket::GestureSource source =
         sequence.front().gesture_source();
+    GestureEventDataPacket::AckState ack_state = sequence.front().ack_state();
+
     if (source != GestureEventDataPacket::TOUCH_TIMEOUT) {
-      // We should handle at most one non-timeout based packet.
-      if (touch_packet_for_current_ack_handled)
+      // We've sent all packets which aren't pending their ack.
+      if (ack_state == GestureEventDataPacket::AckState::PENDING)
         break;
-      state_.OnTouchEventAck(event_consumed, IsTouchStartEvent(source));
-      touch_packet_for_current_ack_handled = true;
+      state_.OnTouchEventAck(sequence.front().ack_state() ==

[jdduke (slow), 2014/11/26 16:07:09]

Nit: (ack_state == GestureEventDataPacket::AckState::CONSUMED)

[tdresser, 2014/11/27 18:26:24]

Done.

+                                 GestureEventDataPacket::AckState::CONSUMED,
+                             IsTouchStartEvent(source));
     }
     // We need to pop the current sequence before sending the packet, because
     // sending the packet could result in this method being re-entered (e.g. on
@@ -206,7 +227,6 @@ void TouchDispositionGestureFilter::OnTouchEventAck(bool event_consumed) {
     sequence.pop();
     FilterAndSendPacket(packet);
   }
-  DCHECK(touch_packet_for_current_ack_handled);

[jdduke (slow), 2014/11/26 16:07:09]

Do we still want to validate that at least one packet was handled?

[tdresser, 2014/11/27 18:26:25]

Done.

 }
 
 bool TouchDispositionGestureFilter::IsEmpty() const {