WIP: Plumbing input event latency reporting through Mus GPU.

ui/events/mojo/latency_info.mojom

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 module ui.mojom;
 
 import "mojo/common/time.mojom";
 import "ui/gfx/geometry/mojo/geometry.mojom";
 
 enum LatencyComponentType {
@@ skipping 71 matching lines @@
 
 struct LatencyComponent {
   // Nondecreasing number that can be used to determine what events happened
   // in the component at the time this struct was sent on to the next
   // component.
   int64 sequence_number;
   // Average time of events that happened in this component.
   mojo.common.mojom.TimeTicks event_time;
   // Count of events that happened in this component
   uint32 event_count;
-  // Time of the oldest event that happened in this component.
+  // TODO(mfomitchev): Do we really need these? We are shipping these cross-IPC
+  // with every frame and for every event for every component. Seems like a lot of
+  // waste
+   // Time of the oldest event that happened in this component.
   mojo.common.mojom.TimeTicks first_event_time;
   // Time of the most recent event that happened in this component.
   mojo.common.mojom.TimeTicks last_event_time;
 };
 
 struct LatencyComponentPair {
   LatencyComponentId key;
   LatencyComponent value;
 };
 
 // See ui/events/latency_info.h
 struct LatencyInfo {
   string trace_name;
   array<LatencyComponentPair> latency_components;
   array<gfx.mojom.PointF> input_coordinates;
   int64 trace_id;
   bool coalesced;
   bool terminated;
 };