Implement scroll handler latency tracking

cc/base/latency_info_swap_promise_monitor.cc

Index: cc/base/latency_info_swap_promise_monitor.cc
diff --git a/cc/base/latency_info_swap_promise_monitor.cc b/cc/base/latency_info_swap_promise_monitor.cc
index 0f2ff7481bb33f86393d754e8fb149d29fdd2b01..d49698708a0768419ccf0c3010deffd4aee7b007 100644
--- a/cc/base/latency_info_swap_promise_monitor.cc
+++ b/cc/base/latency_info_swap_promise_monitor.cc
@@ -9,6 +9,19 @@
 #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(
@@ -21,23 +34,26 @@ LatencyInfoSwapPromiseMonitor::LatencyInfoSwapPromiseMonitor(
 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_)) {
+    scoped_ptr<LatencyInfoSwapPromise> swap_promise(
+        new LatencyInfoSwapPromise(*latency_));
+    layer_tree_host_impl_->QueueSwapPromiseForMainThreadScrollUpdate(
+        swap_promise.Pass());
+  }
+}
+
 }  // namespace cc