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

content/renderer/input/input_event_filter.h

 // 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.
 
 #ifndef CONTENT_RENDERER_INPUT_INPUT_EVENT_FILTER_H_
 #define CONTENT_RENDERER_INPUT_INPUT_EVENT_FILTER_H_
 
 #include <queue>
 #include <set>
 #include <unordered_map>
@@ skipping 48 matching lines @@
   // the thread where the InputEventFilter was constructed.)  The responsibility
   // is left to the eventual handler to deliver the corresponding
   // InputHostMsg_HandleInputEvent_ACK.
   //
   void SetBoundHandler(const Handler& handler) override;
   void DidAddInputHandler(int routing_id) override;
   void DidRemoveInputHandler(int routing_id) override;
   void DidOverscroll(int routing_id,
                      const DidOverscrollParams& params) override;
   void DidStopFlinging(int routing_id) override;
+  void DidStartFlinging(bool is_on_impl) override;
   void NotifyInputEventHandled(int routing_id,
                                blink::WebInputEvent::Type type) override;
 
   // IPC::MessageFilter methods:
   void OnFilterAdded(IPC::Sender* sender) override;
   void OnFilterRemoved() override;
   void OnChannelClosing() override;
   bool OnMessageReceived(const IPC::Message& message) override;
 
   // MainThreadEventQueueClient methods:
@@ skipping 28 matching lines @@
 
   using RouteQueueMap =
       std::unordered_map<int, std::unique_ptr<MainThreadEventQueue>>;
   RouteQueueMap route_queues_;
 
   // Used to intercept overscroll notifications while an event is being
   // dispatched.  If the event causes overscroll, the overscroll metadata can be
   // bundled in the event ack, saving an IPC.  Note that we must continue
   // supporting overscroll IPC notifications due to fling animation updates.
   std::unique_ptr<DidOverscrollParams>* current_overscroll_params_;
+
+  bool is_flinging_on_main_;
+  bool is_flinging_on_impl_;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_INPUT_INPUT_EVENT_FILTER_H_