Add sub-metrics for Event.Latency.TouchToFirstScrollUpdateSwapBegin

content/browser/renderer_host/input/render_widget_host_latency_tracker.cc

Index: content/browser/renderer_host/input/render_widget_host_latency_tracker.cc
diff --git a/content/browser/renderer_host/input/render_widget_host_latency_tracker.cc b/content/browser/renderer_host/input/render_widget_host_latency_tracker.cc
index 17b396efc59e402a93ec18828278032bd22dc3ba..ee595b33c58912e88fc532dd10828f9dae014266 100644
--- a/content/browser/renderer_host/input/render_widget_host_latency_tracker.cc
+++ b/content/browser/renderer_host/input/render_widget_host_latency_tracker.cc
@@ -127,12 +127,70 @@ void ComputeScrollLatencyHistograms(
             original_component, gpu_swap_begin_component);
       }
     }
+
+    // TODO(miletus): Add validation for making sure the following components
+    // are present and their event times are legit.

[tdresser, 2016/08/23 13:57:00]

miletus doesn't work here anymore. 
I assume this is just copied?

We can probably just get rid of this TODO.

[lanwei, 2016/08/24 03:08:28]

Done.

+    LatencyInfo::LatencyComponent rendering_scheduled_component;
+    bool rendering_scheduled_on_main = latency.FindLatency(
+        ui::INPUT_EVENT_LATENCY_RENDERING_SCHEDULED_MAIN_COMPONENT, 0,
+        &rendering_scheduled_component);
+
+    if (!rendering_scheduled_on_main) {
+      if (!latency.FindLatency(
+              ui::INPUT_EVENT_LATENCY_RENDERING_SCHEDULED_IMPL_COMPONENT, 0,
+              &rendering_scheduled_component))
+        goto allScrollUpdate;

[tdresser, 2016/08/23 13:57:00]

Rewrite without using goto.

It's barely mentioned in the style guide, but it's called out as "vanishingly
rare", which is enough to not want to use it.

You could refactor these into a method that returns when a component isn't
found?

[lanwei, 2016/08/24 03:08:28]

Done.

+    }
+
+    if (rendering_scheduled_on_main) {
+      UMA_HISTOGRAM_SCROLL_LATENCY_LONG(
+          "Event.Latency.FirstScrollUpdate.FirstTouchToHandled_Main",
+          original_component, rendering_scheduled_component);
+    } else {
+      UMA_HISTOGRAM_SCROLL_LATENCY_LONG(
+          "Event.Latency.FirstScrollUpdate.FirstTouchToHandled_Impl",
+          original_component, rendering_scheduled_component);
+    }
+
+    LatencyInfo::LatencyComponent renderer_swap_component;
+    if (!latency.FindLatency(ui::INPUT_EVENT_LATENCY_RENDERER_SWAP_COMPONENT, 0,
+                             &renderer_swap_component))
+      goto allScrollUpdate;
+
+    if (rendering_scheduled_on_main) {
+      UMA_HISTOGRAM_SCROLL_LATENCY_LONG(
+          "Event.Latency.FirstScrollUpdate.HandledToRendererSwap_Main",
+          rendering_scheduled_component, renderer_swap_component);
+    } else {
+      UMA_HISTOGRAM_SCROLL_LATENCY_LONG(
+          "Event.Latency.FirstScrollUpdate.HandledToRendererSwap_Impl",
+          rendering_scheduled_component, renderer_swap_component);
+    }
+
+    LatencyInfo::LatencyComponent browser_received_swap_component;
+    if (!latency.FindLatency(
+            ui::INPUT_EVENT_BROWSER_RECEIVED_RENDERER_SWAP_COMPONENT, 0,
+            &browser_received_swap_component))
+      goto allScrollUpdate;
+
+    UMA_HISTOGRAM_SCROLL_LATENCY_SHORT(
+        "Event.Latency.FirstScrollUpdate.RendererSwapToBrowserNotified",
+        renderer_swap_component, browser_received_swap_component);
+
+    UMA_HISTOGRAM_SCROLL_LATENCY_LONG(
+        "Event.Latency.FirstScrollUpdate.BrowserNotifiedToBeforeGpuSwap",
+        browser_received_swap_component, gpu_swap_begin_component);
+
+    UMA_HISTOGRAM_SCROLL_LATENCY_SHORT(
+        "Event.Latency.FirstScrollUpdate.GpuSwap", gpu_swap_begin_component,
+        gpu_swap_end_component);
   } else if (!latency.FindLatency(
                  ui::INPUT_EVENT_LATENCY_SCROLL_UPDATE_ORIGINAL_COMPONENT,
                  latency_component_id, &original_component)) {
     return;
   }
 
+allScrollUpdate:
   // This UMA metric tracks the time from when the original touch event is
   // created to when the scroll gesture results in final frame swap.
   for (size_t i = 0; i < original_component.event_count; i++) {
@@ -158,7 +216,6 @@ void ComputeScrollLatencyHistograms(
   bool rendering_scheduled_on_main = latency.FindLatency(
       ui::INPUT_EVENT_LATENCY_RENDERING_SCHEDULED_MAIN_COMPONENT,
       0, &rendering_scheduled_component);
-
   if (!rendering_scheduled_on_main) {
     if (!latency.FindLatency(
             ui::INPUT_EVENT_LATENCY_RENDERING_SCHEDULED_IMPL_COMPONENT,