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

content/renderer/input/input_event_filter.h

Index: content/renderer/input/input_event_filter.h
diff --git a/content/renderer/input/input_event_filter.h b/content/renderer/input/input_event_filter.h
index 6457fb6116ceff1fa2fe81b10fc0632ad08bb7dd..3a18c186f4c68f56d64f229d4d33c7d8919a4fa3 100644
--- a/content/renderer/input/input_event_filter.h
+++ b/content/renderer/input/input_event_filter.h
@@ -81,6 +81,9 @@ class CONTENT_EXPORT InputEventFilter : public InputHandlerManagerClient,
                              const ui::LatencyInfo& latency,
                              InputEventDispatchType dispatch_type) override;
 
+  // Whether the fling animation is happening right now.
+  void SetIsFlinging(bool is_flinging) override;
+
  private:
   ~InputEventFilter() override;
 
@@ -114,6 +117,8 @@ class CONTENT_EXPORT InputEventFilter : public InputHandlerManagerClient,
   // 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_;
 };
 
 }  // namespace content