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

content/browser/renderer_host/render_widget_host_impl.cc

Index: content/browser/renderer_host/render_widget_host_impl.cc
diff --git a/content/browser/renderer_host/render_widget_host_impl.cc b/content/browser/renderer_host/render_widget_host_impl.cc
index c02b51aeef383a7dec78d64262fea8961339d576..cece57a1412987df052eb9fc374f122ed6fab8f6 100644
--- a/content/browser/renderer_host/render_widget_host_impl.cc
+++ b/content/browser/renderer_host/render_widget_host_impl.cc
@@ -91,6 +91,10 @@ namespace {
 
 bool g_check_for_pending_resize_ack = true;
 
+const size_t kBrowserCompositeLatencyHistorySize = 60;
+const double kBrowserCompositeLatencyEstimationPercentile = 90.0;
+const double kBrowserCompositeLatencyEstimationSlack = 1.1;
+
 typedef std::pair<int32, int32> RenderWidgetHostID;
 typedef base::hash_map<RenderWidgetHostID, RenderWidgetHostImpl*>
     RoutingIDWidgetMap;
@@ -184,6 +188,7 @@ RenderWidgetHostImpl::RenderWidgetHostImpl(RenderWidgetHostDelegate* delegate,
       allow_privileged_mouse_lock_(false),
       has_touch_handler_(false),
       next_browser_snapshot_id_(1),
+      browser_composite_latency_history_(kBrowserCompositeLatencyHistorySize),
       weak_factory_(this) {
   CHECK(delegate_);
   if (routing_id_ == MSG_ROUTING_NONE) {
@@ -1438,6 +1443,9 @@ bool RenderWidgetHostImpl::OnSwapCompositorFrame(
   input_router_->OnViewUpdated(
       GetInputRouterViewFlagsFromCompositorFrameMetadata(frame->metadata));
 
+  for (auto& latency : frame->metadata.latency_info)
+    latency.AddLatencyNumber(ui::INPUT_EVENT_BROWSER_COMPOSITE_COMPONENT, 0, 0);
+
   if (view_) {
     view_->OnSwapCompositorFrame(output_surface_id, frame.Pass());
     view_->DidReceiveRendererFrame();
@@ -2011,6 +2019,21 @@ void RenderWidgetHostImpl::FrameSwapped(const ui::LatencyInfo& latency_info) {
   }
 
   latency_tracker_.OnFrameSwapped(latency_info);
+
+  ui::LatencyInfo::LatencyComponent gpu_swap_component;
+  if (!latency_info.FindLatency(
+          ui::INPUT_EVENT_GPU_SWAP_BUFFER_COMPONENT, 0, &gpu_swap_component)) {
+    return;
+  }
+
+  ui::LatencyInfo::LatencyComponent composite_component;
+  if (latency_info.FindLatency(ui::INPUT_EVENT_BROWSER_COMPOSITE_COMPONENT,
+                               0,
+                               &composite_component)) {
+    base::TimeDelta delta =
+        gpu_swap_component.event_time - composite_component.event_time;
+    browser_composite_latency_history_.InsertSample(delta);
+  }
 }
 
 void RenderWidgetHostImpl::DidReceiveRendererFrame() {
@@ -2157,6 +2180,17 @@ BrowserAccessibilityManager*
       delegate_->GetOrCreateRootBrowserAccessibilityManager() : NULL;
 }
 
+base::TimeDelta RenderWidgetHostImpl::GetEstimatedBrowserCompositeTime() {
+  // TODO(brianderson): Remove lower bound on estimate once we're sure it won't
+  // cause regressions.
+  return std::max(
+      browser_composite_latency_history_.Percentile(
+          kBrowserCompositeLatencyEstimationPercentile) *
+          kBrowserCompositeLatencyEstimationSlack,
+      base::TimeDelta::FromMicroseconds(
+          (1.0f * base::Time::kMicrosecondsPerSecond) / (3.0f * 60)));
+}
+
 #if defined(OS_WIN)
 gfx::NativeViewAccessible
     RenderWidgetHostImpl::GetParentNativeViewAccessible() {