Add Keyboard Latency UMA Metrics.

ui/latency/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 61 matching lines @@
   // but the swap failed.
   INPUT_EVENT_LATENCY_TERMINATED_SWAP_FAILED_COMPONENT,
   LATENCY_COMPONENT_TYPE_LAST =
       INPUT_EVENT_LATENCY_TERMINATED_SWAP_FAILED_COMPONENT,
 };
 
 enum SourceEventType {
   UNKNOWN,
   WHEEL,
   TOUCH,
+  KEY_PRESS,
   OTHER,
   SOURCE_EVENT_TYPE_LAST = OTHER,
 };
 
 struct LatencyComponentId {
   LatencyComponentType type;
   int64 id;
 };
 
 struct LatencyComponent {
@@ skipping 18 matching lines @@
 
 // See ui/latency/latency_info.h
 struct LatencyInfo {
   string trace_name;
   array<LatencyComponentPair> latency_components;
   int64 trace_id;
   bool coalesced;
   bool terminated;
   SourceEventType source_event_type;
 };