WIP: Plumbing input event latency reporting through Mus GPU.

content/browser/renderer_host/input/render_widget_host_latency_tracker.h

Index: content/browser/renderer_host/input/render_widget_host_latency_tracker.h
diff --git a/content/browser/renderer_host/input/render_widget_host_latency_tracker.h b/content/browser/renderer_host/input/render_widget_host_latency_tracker.h
index e4147b9052ff3a76134d2f39e4be0237f5d38e8b..8f5f29ca3dea0a2fd57ca8cbd45fe5846b0f00a5 100644
--- a/content/browser/renderer_host/input/render_widget_host_latency_tracker.h
+++ b/content/browser/renderer_host/input/render_widget_host_latency_tracker.h
@@ -10,6 +10,7 @@
 #include <vector>
 
 #include "base/macros.h"
+#include "components/latency_tracker/latency_tracker.h"
 #include "content/browser/renderer_host/event_with_latency_info.h"
 #include "content/common/content_export.h"
 #include "content/common/input/input_event_ack_state.h"
@@ -21,7 +22,8 @@ class RenderWidgetHostDelegate;
 
 // Utility class for tracking the latency of events passing through
 // a given RenderWidgetHost.
-class CONTENT_EXPORT RenderWidgetHostLatencyTracker {
+class CONTENT_EXPORT RenderWidgetHostLatencyTracker
+    : latency_tracker::LatencyTracker {
  public:
   explicit RenderWidgetHostLatencyTracker();
   ~RenderWidgetHostLatencyTracker();
@@ -75,6 +77,12 @@ class CONTENT_EXPORT RenderWidgetHostLatencyTracker {
   void SetDelegate(RenderWidgetHostDelegate*);
 
  private:
+  // latency_tracker::LatencyTracker:
+  void ReportRapporScrollLatency(
+      const std::string& name,
+      const ui::LatencyInfo::LatencyComponent& start_component,
+      const ui::LatencyInfo::LatencyComponent& end_component) override;
+
   int64_t last_event_id_;
   int64_t latency_component_id_;
   float device_scale_factor_;