Break down end-to-end scroll update latency UMA metrics

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 dc2873988b3ef97b6bb355712e6adf13e68e4074..3ba44a207f75e19267d0b7753310df9763a1629f 100644
--- a/cc/base/latency_info_swap_promise_monitor.cc
+++ b/cc/base/latency_info_swap_promise_monitor.cc
@@ -12,12 +12,14 @@
 
 namespace {
 
-bool AddRenderingScheduledComponent(ui::LatencyInfo* latency_info) {
-  if (latency_info->FindLatency(
-          ui::INPUT_EVENT_LATENCY_RENDERING_SCHEDULED_COMPONENT, 0, nullptr))
+bool AddRenderingScheduledComponent(ui::LatencyInfo* latency_info,
+                                    bool on_main) {
+  ui::LatencyComponentType type = on_main ?
+      ui::INPUT_EVENT_LATENCY_RENDERING_SCHEDULED_MAIN_COMPONENT :
+      ui::INPUT_EVENT_LATENCY_RENDERING_SCHEDULED_IMPL_COMPONENT;
+  if (latency_info->FindLatency(type, 0, nullptr))
     return false;
-  latency_info->AddLatencyNumber(
-      ui::INPUT_EVENT_LATENCY_RENDERING_SCHEDULED_COMPONENT, 0, 0);
+  latency_info->AddLatencyNumber(type, 0, 0);
   return true;
 }
 
@@ -48,14 +50,14 @@ LatencyInfoSwapPromiseMonitor::LatencyInfoSwapPromiseMonitor(
 LatencyInfoSwapPromiseMonitor::~LatencyInfoSwapPromiseMonitor() {}
 
 void LatencyInfoSwapPromiseMonitor::OnSetNeedsCommitOnMain() {
-  if (AddRenderingScheduledComponent(latency_)) {
+  if (AddRenderingScheduledComponent(latency_, true)) {

[danakj, 2015/02/11 23:38:24]

use a comment or a temp bool to give this literal a name
like
..., true /* on_main */);
or 
bool on_main = true;
... , on_main);

[Yufeng Shen (Slow to review), 2015/02/12 02:59:02]

Done.

     scoped_ptr<SwapPromise> swap_promise(new LatencyInfoSwapPromise(*latency_));
     layer_tree_host_->QueueSwapPromise(swap_promise.Pass());
   }
 }
 
 void LatencyInfoSwapPromiseMonitor::OnSetNeedsRedrawOnImpl() {
-  if (AddRenderingScheduledComponent(latency_)) {
+  if (AddRenderingScheduledComponent(latency_, false)) {

[danakj, 2015/02/11 23:38:24]

dittos

[Yufeng Shen (Slow to review), 2015/02/12 02:59:02]

Done.

     scoped_ptr<SwapPromise> swap_promise(new LatencyInfoSwapPromise(*latency_));
     layer_tree_host_impl_->active_tree()->QueueSwapPromise(swap_promise.Pass());
   }