Routes touch ACK events to the correct GestureProvider

ui/events/gestures/gesture_recognizer_impl.h

 // 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.
 
 #ifndef UI_EVENTS_GESTURES_GESTURE_RECOGNIZER_IMPL_H_
 #define UI_EVENTS_GESTURES_GESTURE_RECOGNIZER_IMPL_H_
 
 #include <stdint.h>
 
 #include <map>
@@ skipping 70 matching lines @@
   // Overridden from GestureProviderAuraClient
   void OnGestureEvent(GestureConsumer* raw_input_consumer,
                       GestureEvent* event) override;
 
   // Convenience method to find the GestureEventHelper that can dispatch events
   // to a specific |consumer|.
   GestureEventHelper* FindDispatchHelperForConsumer(GestureConsumer* consumer);
   std::map<GestureConsumer*, std::unique_ptr<GestureProviderAura>>
       consumer_gesture_provider_;
 
+  // Maps an event via its |unique_event_id| to the corresponding gesture
+  // provider. This avoids any invalid reference while routing ACK for events

[tdresser, 2017/04/06 20:59:52]

ACK -> ACKs

[malaykeshav, 2017/04/07 01:07:59]

Doesnt each event have just 1 ACK?

[tdresser, 2017/04/07 12:33:00]

Yes, but you're referring to "events" and events have ACKs.

Any of:
"while routing an event's ACK" or
"while routing ACKs for events"

or even just:
"while routing an ACK"

would be fine.

+  // that may arise post |TransferEventsTo()| function call.
+  // See http://crbug.com/698843 for more info.
+  std::map<uint32_t, GestureProviderAura*> event_to_gesture_provider_;
+
   // |touch_id_target_| maps a touch-id to its target window.
   // touch-ids are removed from |touch_id_target_| on
   // ET_TOUCH_RELEASE and ET_TOUCH_CANCEL.
   TouchIdToConsumerMap touch_id_target_;
 
   std::vector<GestureEventHelper*> helpers_;
 
   DISALLOW_COPY_AND_ASSIGN(GestureRecognizerImpl);
 };
 
 // Provided only for testing:
 EVENTS_EXPORT void SetGestureRecognizerForTesting(
     GestureRecognizer* gesture_recognizer);
 
 }  // namespace ui
 
 #endif  // UI_EVENTS_GESTURES_GESTURE_RECOGNIZER_IMPL_H_