Add TimeToScrollUpdateSwapBegin2 to UKM

ui/latency/latency_tracker.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 UI_LATENCY_LATENCY_TRACKER_H_
 #define UI_LATENCY_LATENCY_TRACKER_H_
 
 #include "base/macros.h"
 #include "ui/latency/latency_info.h"
 
@@ skipping 10 matching lines @@
   // performing relevant UMA latency reporting.
   // Called when GPU buffers swap completes.
   void OnGpuSwapBuffersCompleted(const LatencyInfo& latency);
 
  protected:
   virtual void ReportRapporScrollLatency(
       const std::string& name,
       const LatencyInfo::LatencyComponent& start_component,
       const LatencyInfo::LatencyComponent& end_component);
 
+  virtual void ReportUkmScrollLatency(
+      const std::string& event_name,
+      const std::string& metric_name,
+      const LatencyInfo::LatencyComponent& start_component,
+      const LatencyInfo::LatencyComponent& end_component);
+
  private:
   void ComputeEndToEndLatencyHistograms(
       const LatencyInfo::LatencyComponent& gpu_swap_begin_component,
       const LatencyInfo::LatencyComponent& gpu_swap_end_component,
       const LatencyInfo& latency);
 
   DISALLOW_COPY_AND_ASSIGN(LatencyTracker);
 };
 
 }  // namespace latency
 
 #endif  // UI_LATENCY_LATENCY_TRACKER_H_