Fix recursion in handling touch input events acks.

content/browser/renderer_host/input/passthrough_touch_event_queue.h

 // Copyright 2017 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 CONTENT_BROWSER_RENDERER_HOST_INPUT_PASSTHROUGH_TOUCH_EVENT_QUEUE_H_
 #define CONTENT_BROWSER_RENDERER_HOST_INPUT_PASSTHROUGH_TOUCH_EVENT_QUEUE_H_
 
 #include "content/browser/renderer_host/input/touch_event_queue.h"
 
 #include <set>
@@ skipping 103 matching lines @@
   // current sequence. This is only used when the event is synthetically
   // cancelled after a touch timeout.
   bool drop_remaining_touches_in_sequence_;
 
   // Optional handler for timed-out touch event acks.
   std::unique_ptr<TouchTimeoutHandler> timeout_handler_;
 
   // Whether touch events should be sent as uncancelable or not.
   bool send_touch_events_async_;
 
+  bool processing_acks_;
+
   // Event is saved to compare pointer positions for new touchmove events.
   std::unique_ptr<blink::WebTouchEvent> last_sent_touchevent_;
 
   // Stores outstanding touches that have been sent to the renderer but have
   // not yet been ack'd by the renderer. The set is explicitly ordered based
   // on the unique touch event id.
   std::set<TouchEventWithLatencyInfoAndAckState> outstanding_touches_;
 
   DISALLOW_COPY_AND_ASSIGN(PassthroughTouchEventQueue);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_INPUT_PASSTHROUGH_TOUCH_EVENT_QUEUE_H_