Implement scroll handler latency tracking

cc/base/latency_info_swap_promise_monitor.cc

 // Copyright 2013 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.
 
 #include "cc/base/latency_info_swap_promise_monitor.h"
 
 #include "cc/base/latency_info_swap_promise.h"
 #include "cc/trees/layer_tree_host.h"
 #include "cc/trees/layer_tree_host_impl.h"
 #include "cc/trees/layer_tree_impl.h"
 
+namespace {
+
+bool AddRenderingScheduledComponent(ui::LatencyInfo* latency_info) {
+  if (latency_info->FindLatency(
+          ui::INPUT_EVENT_LATENCY_RENDERING_SCHEDULED_COMPONENT, 0, 0))
+    return false;
+  latency_info->AddLatencyNumber(
+      ui::INPUT_EVENT_LATENCY_RENDERING_SCHEDULED_COMPONENT, 0, 0);
+  return true;
+}
+
+}  // namespace
+
 namespace cc {
 
 LatencyInfoSwapPromiseMonitor::LatencyInfoSwapPromiseMonitor(
     ui::LatencyInfo* latency,
     LayerTreeHost* layer_tree_host,
     LayerTreeHostImpl* layer_tree_host_impl)
     : SwapPromiseMonitor(layer_tree_host, layer_tree_host_impl),
       latency_(latency) {}
 
 LatencyInfoSwapPromiseMonitor::~LatencyInfoSwapPromiseMonitor() {}
 
 void LatencyInfoSwapPromiseMonitor::OnSetNeedsCommitOnMain() {
-  if (!latency_->FindLatency(
-          ui::INPUT_EVENT_LATENCY_RENDERING_SCHEDULED_COMPONENT, 0, 0)) {
-    latency_->AddLatencyNumber(
-        ui::INPUT_EVENT_LATENCY_RENDERING_SCHEDULED_COMPONENT, 0, 0);
+  if (AddRenderingScheduledComponent(latency_)) {
     scoped_ptr<SwapPromise> swap_promise(new LatencyInfoSwapPromise(*latency_));
     layer_tree_host_->QueueSwapPromise(swap_promise.Pass());
   }
 }
 
 void LatencyInfoSwapPromiseMonitor::OnSetNeedsRedrawOnImpl() {
-  if (!latency_->FindLatency(
-          ui::INPUT_EVENT_LATENCY_RENDERING_SCHEDULED_COMPONENT, 0, 0)) {
-    latency_->AddLatencyNumber(
-        ui::INPUT_EVENT_LATENCY_RENDERING_SCHEDULED_COMPONENT, 0, 0);
+  if (AddRenderingScheduledComponent(latency_)) {
     scoped_ptr<SwapPromise> swap_promise(new LatencyInfoSwapPromise(*latency_));
     layer_tree_host_impl_->active_tree()->QueueSwapPromise(swap_promise.Pass());
   }
 }
 
+void LatencyInfoSwapPromiseMonitor::OnForwardScrollUpdateToMainThreadOnImpl() {
+  if (AddRenderingScheduledComponent(latency_))
+    layer_tree_host_impl_->QueueScrollUpdateLatencyInfo(*latency_);
+}
+
 }  // namespace cc