Add telemetry to track the time an event spent waiting for the main thread.

ui/base/latency_info.h

Index: ui/base/latency_info.h
diff --git a/ui/base/latency_info.h b/ui/base/latency_info.h
index 3482a500a8d0d85a89a5e92d92e7faf14f0be34e..65c23b4343ae6b444cdc5834d6b1e3d2a67596ca 100644
--- a/ui/base/latency_info.h
+++ b/ui/base/latency_info.h
@@ -32,7 +32,11 @@ enum LatencyComponentType {
   INPUT_EVENT_LATENCY_UI_COMPONENT,
   // Timestamp when the event is acked from renderer. This is currently set
   // only for touch events.
-  INPUT_EVENT_LATENCY_ACKED_COMPONENT
+  INPUT_EVENT_LATENCY_ACKED_COMPONENT,
+  // Timestamp when the event is sent from the impl to main renderer thread.
+  INPUT_EVENT_LATENCY_EVENT_SENT_FROM_IMPL_THREAD_COMPONENT,
+  // Timestamp when the event is received on the main thread.
+  INPUT_EVENT_LATENCY_EVENT_RECEIVED_ON_MAIN_THREAD_COMPONENT,
 };
 
 struct UI_EXPORT LatencyInfo {