Adding source_event_type to LatencyInfo mojom

ui/latency/mojo/latency_info.mojom

Index: ui/latency/mojo/latency_info.mojom
diff --git a/ui/latency/mojo/latency_info.mojom b/ui/latency/mojo/latency_info.mojom
index 5b40d32960058498313097ef8c9b2c45dff06a63..0b985e2ff003366b973e500aeb5e87438db6ad45 100644
--- a/ui/latency/mojo/latency_info.mojom
+++ b/ui/latency/mojo/latency_info.mojom
@@ -75,6 +75,14 @@ enum LatencyComponentType {
       INPUT_EVENT_LATENCY_TERMINATED_SWAP_FAILED_COMPONENT,
 };
 
+enum SourceEventType {
+  UNKNOWN,
+  WHEEL,
+  TOUCH,
+  OTHER,
+  SOURCE_EVENT_TYPE_LAST = OTHER,

[tdresser, 2017/04/27 14:39:27]

Is there some assertion we can add to reduce the risk of these (and the
LatencyComponentType) getting out of sync with latency_info.h?

[mfomitchev, 2017/04/27 22:06:28]

What if we add an assert for ui::mojom::LATENCY_COMPONENT_TYPE_LAST matching
ui::LATENCY_COMPONENT_TYPE_LAST and a similar one for SOURCE_EVENT_TYPE_LAST in
latency_info_struct_traits.h?

tsepez@: Interested in your thoughts as well. Are we doing anything like this
elsewhere?

[Fady Samuel, 2017/04/27 22:49:25]

We deal with this problem in cc via SetAll/SetNew usage. Basically, you can't
much around with things directly

+};
+
 struct LatencyComponentId {
   LatencyComponentType type;
   int64 id;
@@ -107,4 +115,5 @@ struct LatencyInfo {
   int64 trace_id;
   bool coalesced;
   bool terminated;
+  SourceEventType source_event_type;
 };