Add new latency_info for tracking browser composite time.

ui/events/latency_info.h

Index: ui/events/latency_info.h
diff --git a/ui/events/latency_info.h b/ui/events/latency_info.h
index 92d928d615837d1323f07112b9244c135af4e67d..7915c96c24a056a4b621f6fd77b44e4be30f5e35 100644
--- a/ui/events/latency_info.h
+++ b/ui/events/latency_info.h
@@ -54,6 +54,13 @@ enum LatencyComponentType {
   WINDOW_OLD_SNAPSHOT_FRAME_NUMBER_COMPONENT,
   // Timestamp when a tab is requested to be shown.
   TAB_SHOW_COMPONENT,
+  // Timestamp of when the browser began compositing
+  INPUT_EVENT_BROWSER_COMPOSITE_COMPONENT,

[jbauman, 2014/09/19 20:40:29]

These don't really have anything to do with input events, so I don't think we
should have INPUT_EVENT in the name.

[orglofch, 2014/09/19 22:40:27]

Technically the events are still tied to input in that latency_info only has
input related begin components. I was planning on renaming these in a later
patch once I've added per frame latency_info.

+  // Timestamp of when an unparented output surface began swap buffers

[brianderson, 2014/09/18 23:26:15]

"an uparented output surface" -> "the Browser process"

[orglofch, 2014/09/19 22:40:27]

Done.

+  INPUT_EVENT_OUTPUT_SURFACE_SWAP_BUFFER_COMPONENT,

[brianderson, 2014/09/18 23:26:15]

INPUT_EVENT_BROWSER_SWAP_BUFFER_COMPONENT?

[orglofch, 2014/09/19 22:40:27]

Done.

+  // Timestamp of when the gpu service began swap buffers, unlike
+  // INPUT_EVENT_LATENCY_TERMINATED_FRAME_SWAP_COMPONENT which measure after
+  INPUT_EVENT_GPU_SWAP_BUFFER_COMPONENT,
   // ---------------------------TERMINAL COMPONENT-----------------------------
   // TERMINAL COMPONENT is when we show the latency end in chrome://tracing.
   // Timestamp when the mouse event is acked from renderer and it does not