Add UMA metric for tracking listeners for blocking touch while fling is happening

content/browser/renderer_host/input/input_router_impl.cc

 // Copyright 2013 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.
 
 #include "content/browser/renderer_host/input/input_router_impl.h"
 
 #include <math.h>
 
 #include <utility>
 
@@ skipping 44 matching lines @@
     case INPUT_EVENT_ACK_STATE_NOT_CONSUMED: return "NOT_CONSUMED";
     case INPUT_EVENT_ACK_STATE_NO_CONSUMER_EXISTS: return "NO_CONSUMER_EXISTS";
     case INPUT_EVENT_ACK_STATE_IGNORED: return "IGNORED";
     case INPUT_EVENT_ACK_STATE_SET_NON_BLOCKING:
       return "SET_NON_BLOCKING";
   }
   DLOG(WARNING) << "Unhandled InputEventAckState in GetEventAckName.";
   return "";
 }
 
+enum TouchEventDispatchResultType {
+  UNHANDLED_TOUCHES,  //  Unhandled touch events.
+  HANDLED_TOUCHES,    // Handled touch events.
+  TOUCH_EVENT_DISPATCH_RESULT_TYPE_COUNT
+};
+
 } // namespace
 
 InputRouterImpl::Config::Config() {
 }
 
 InputRouterImpl::InputRouterImpl(IPC::Sender* sender,
                                  InputRouterClient* client,
                                  InputAckHandler* ack_handler,
                                  int routing_id,
                                  const Config& config)
@@ skipping 372 matching lines @@
   // Log the time delta for processing an input event.
   TimeDelta delta = TimeTicks::Now() - input_event_start_time_;
   UMA_HISTOGRAM_TIMES("MPArch.IIR_InputEventDelta", delta);
 
   if (ack.overscroll) {
     DCHECK(ack.type == WebInputEvent::MouseWheel ||
            ack.type == WebInputEvent::GestureScrollUpdate);
     OnDidOverscroll(*ack.overscroll);
   }
 
+  // Count the canceled touch starts while there is an active fling animation.
+  if (gesture_event_queue_.FlingInProgress() &&
+      ack.type == WebInputEvent::TouchStart) {
+    TouchEventDispatchResultType result =
+        (ack.state == INPUT_EVENT_ACK_STATE_CONSUMED) ? HANDLED_TOUCHES

[dtapuska, 2016/04/27 19:05:13]

I presume the passive ones counted as unhandled is ok. Do we want to call the
passive ones out to see it increase so we can see the intervention taking place?

+                                                      : UNHANDLED_TOUCHES;
+    UMA_HISTOGRAM_ENUMERATION("Event.Touch.TouchStartsCanceledDuringFling",
+                              result, TOUCH_EVENT_DISPATCH_RESULT_TYPE_COUNT);
+  }
+
   ProcessInputEventAck(ack.type, ack.state, ack.latency,
                        ack.unique_touch_event_id, RENDERER);
 }
 
 void InputRouterImpl::OnDidOverscroll(const DidOverscrollParams& params) {
   client_->DidOverscroll(params);
 }
 
 void InputRouterImpl::OnMsgMoveCaretAck() {
   move_caret_pending_ = false;
@@ skipping 172 matching lines @@
 
   flush_requested_ = false;
   client_->DidFlush();
 }
 
 void InputRouterImpl::SetFrameTreeNodeId(int frameTreeNodeId) {
   frame_tree_node_id_ = frameTreeNodeId;
 }
 
 }  // namespace content