Buffer cross frame paint timing updates.

chrome/renderer/page_load_metrics/metrics_render_frame_observer.h

 // Copyright 2015 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 CHROME_RENDERER_PAGE_LOAD_METRICS_METRICS_RENDER_FRAME_OBSERVER_H_
 #define CHROME_RENDERER_PAGE_LOAD_METRICS_METRICS_RENDER_FRAME_OBSERVER_H_
 
 #include <memory>
 
 #include "base/macros.h"
@@ skipping 29 matching lines @@
   void OnDestruct() override;
 
   // Invoked when a frame is going away. This is our last chance to send IPCs
   // before being destroyed.
   void FrameDetached() override;
 
  private:
   void SendMetrics();
   virtual bool ShouldSendMetrics() const;
   virtual mojom::PageLoadTimingPtr GetTiming() const;
-  virtual std::unique_ptr<base::Timer> CreateTimer() const;
+  virtual std::unique_ptr<base::Timer> CreateTimer();
   virtual std::unique_ptr<PageTimingSender> CreatePageTimingSender();
   virtual bool HasNoRenderFrame() const;
 
   // Will be null when we're not actively sending metrics.
   std::unique_ptr<PageTimingMetricsSender> page_timing_metrics_sender_;
 
   DISALLOW_COPY_AND_ASSIGN(MetricsRenderFrameObserver);
 };
 
 }  // namespace page_load_metrics
 
 #endif  // CHROME_RENDERER_PAGE_LOAD_METRICS_METRICS_RENDER_FRAME_OBSERVER_H_