Reland "Add new latency_info for tracking browser composite time."

content/browser/renderer_host/render_widget_host_latency_tracker.h

 // Copyright 2014 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_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_LATENCY_TRACKER_H_
 #define CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_LATENCY_TRACKER_H_
 
 #include <vector>
 
 #include "base/basictypes.h"
+#include "cc/base/rolling_time_delta_history.h"
 #include "content/browser/renderer_host/event_with_latency_info.h"
 #include "content/common/content_export.h"
 #include "ui/events/latency_info.h"
 
 namespace content {
 
 // Utility class for tracking the latency of events passing through
 // a given RenderWidgetHost.
 class CONTENT_EXPORT RenderWidgetHostLatencyTracker {
  public:
@@ skipping 20 matching lines @@
   // Populates renderer-created LatencyInfo entries with the appropriate latency
   // component id. Called when the RenderWidgetHost receives a compositor swap
   // update from the renderer.
   void OnSwapCompositorFrame(std::vector<ui::LatencyInfo>* latencies);
 
   // Terminates latency tracking for events that triggered rendering, also
   // performing relevant UMA latency reporting.
   // Called when the RenderWidgetHost receives a swap update from the GPU.
   void OnFrameSwapped(const ui::LatencyInfo& latency);
 
+  // Produces an estimate of the time between browser composite and GPU swap,
+  // as informed by historical latency values.
+  base::TimeDelta GetEstimatedBrowserCompositeTime() const;
+
   // WebInputEvent coordinates are in DPIs, while LatencyInfo expects
   // coordinates in device pixels.
   void set_device_scale_factor(float device_scale_factor) {
     device_scale_factor_ = device_scale_factor;
   }
 
   // Returns the ID that uniquely describes this component to the latency
   // subsystem.
   int64 latency_component_id() const { return latency_component_id_; }
 
  private:
   int64 last_event_id_;
   int64 latency_component_id_;
   float device_scale_factor_;
+  cc::RollingTimeDeltaHistory browser_composite_latency_history_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderWidgetHostLatencyTracker);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_LATENCY_TRACKER_H_