Test path to dump dispatch/ack sequence at TouchEventQueue.

content/browser/renderer_host/input/touch_event_queue.cc

Index: content/browser/renderer_host/input/touch_event_queue.cc
diff --git a/content/browser/renderer_host/input/touch_event_queue.cc b/content/browser/renderer_host/input/touch_event_queue.cc
index 66023b1e9cbdb980d194f2a7d20814d2154bea27..1aeb105f6a0be8eaa5b9cdfaf7f7050db6198a1b 100644
--- a/content/browser/renderer_host/input/touch_event_queue.cc
+++ b/content/browser/renderer_host/input/touch_event_queue.cc
@@ -496,6 +496,10 @@ void TouchEventQueue::ProcessTouchAck(InputEventAckState ack_result,
                                       const uint32_t unique_touch_event_id) {
   TRACE_EVENT0("input", "TouchEventQueue::ProcessTouchAck");
 
+  LOG(ERROR) << "======= mDebug " << __FUNCTION__
+             << " id=" << unique_touch_event_id
+             << " |q| = " << touch_queue_.size();
+
   // We receive an ack for async touchmove from render.
   if (!ack_pending_async_touchmove_ids_.empty() &&
       ack_pending_async_touchmove_ids_.front() == unique_touch_event_id) {
@@ -779,6 +783,11 @@ void TouchEventQueue::SendTouchEventImmediately(
 
   base::AutoReset<bool> dispatching_touch(&dispatching_touch_, true);
 
+  LOG(ERROR) << "======= mDebug " << __FUNCTION__
+             << " type=" << WebInputEventTraits::GetName(touch->event.type)
+             << " id=" << touch->event.uniqueTouchEventId
+             << " |q| = " << touch_queue_.size();
+
   client_->SendTouchEventImmediately(*touch);
 
   // A synchronous ack will reset |dispatching_touch_|, in which case the touch