Add Keyboard Latency UMA Metrics.

tools/metrics/histograms/histograms.xml

Index: tools/metrics/histograms/histograms.xml
diff --git a/tools/metrics/histograms/histograms.xml b/tools/metrics/histograms/histograms.xml
index 501b53f02692329842cb406981d369220b57c45e..e7736d5bcf3afc6049d87803a3f2a741483d88f4 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -15987,6 +15987,26 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Event.Latency.BlockingTime.KeyPressDefaultAllowed" units="ms">
+  <owner>tdresser@chromium.org</owner>
+  <owner>input-dev@chromium.org</owner>
+  <summary>
+    Time between the renderer main thread receiving a keyboard event and acking
+    it, for events which were not preventDefaulted. Only recorded for key
+    presses.
+  </summary>
+</histogram>
+
+<histogram name="Event.Latency.BlockingTime.KeyPressDefaultPrevented"
+    units="ms">
+  <owner>tdresser@chromium.org</owner>
+  <owner>input-dev@chromium.org</owner>
+  <summary>
+    Time between the renderer main thread receiving a keyboard event and acking
+    it, for events which were preventDefaulted. Only recorded for key presses.
+  </summary>
+</histogram>
+
 <histogram name="Event.Latency.BlockingTime.TouchEndDefaultAllowed" units="ms">
   <owner>tdresser@chromium.org</owner>
   <summary>
@@ -16413,6 +16433,24 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Event.Latency.Browser.KeyPressAcked" units="microseconds">
+  <owner>tdresser@chromium.org</owner>
+  <owner>input-dev@chromium.org</owner>
+  <summary>
+    Time between key events sent from RWH to renderer and acked by renderer.
+    Only monitors key presses.
+  </summary>
+</histogram>
+
+<histogram name="Event.Latency.Browser.KeyPressUI" units="microseconds">
+  <owner>tdresser@chromium.org</owner>
+  <owner>input-dev@chromium.org</owner>
+  <summary>
+    Time between key events received by Chrome and sent from RWH to renderer.
+    Only monitors key presses.
+  </summary>
+</histogram>
+
 <histogram name="Event.Latency.Browser.TouchAcked" units="microseconds">
   <owner>tdresser@chromium.org</owner>
   <summary>
@@ -16449,6 +16487,16 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Event.Latency.EndToEnd.Key" units="ms">
+  <owner>tdresser@chromium.org</owner>
+  <owner>input-dev@chromium.org</owner>
+  <summary>
+    Time between the OS receiving a keyboard event and the resulting GPU frame
+    swap. If no swap was induced by the event, no recording is made. Only
+    recorded for key presses.
+  </summary>
+</histogram>
+
 <histogram name="Event.Latency.HitTest" units="microseconds">
   <owner>dtapuska@chromium.org</owner>
   <summary>
@@ -16476,6 +16524,27 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <summary>Time between input event received by OS and sent to Chrome.</summary>
 </histogram>
 
+<histogram name="Event.Latency.QueueingTime.KeyPressDefaultAllowed" units="ms">
+  <owner>tdresser@chromium.org</owner>
+  <owner>input-dev@chromium.org</owner>
+  <summary>
+    Time between sending a keyboard event to the renderer main thread and when
+    the renderer begins to process that event, for events which were not
+    preventDefaulted. Only recorded for key presses.
+  </summary>
+</histogram>
+
+<histogram name="Event.Latency.QueueingTime.KeyPressDefaultPrevented"
+    units="ms">
+  <owner>tdresser@chromium.org</owner>
+  <owner>input-dev@chromium.org</owner>
+  <summary>
+    Time between sending a keyboard event to the renderer main thread and when
+    the renderer begins to process that event, for events which were
+    preventDefaulted. Only recorded for key presses.
+  </summary>
+</histogram>
+
 <histogram name="Event.Latency.QueueingTime.TouchEndDefaultAllowed" units="ms">
   <owner>tdresser@chromium.org</owner>
   <summary>