Add Keyboard Latency UMA Metrics.

chrome/browser/chromeos/accessibility/event_handler_common.cc

Index: chrome/browser/chromeos/accessibility/event_handler_common.cc
diff --git a/chrome/browser/chromeos/accessibility/event_handler_common.cc b/chrome/browser/chromeos/accessibility/event_handler_common.cc
index d1da17a19bf501dfe16995569783a34281ea51a8..3a55d8b92076a732c1193d9e8ad2da61bea40acb 100644
--- a/chrome/browser/chromeos/accessibility/event_handler_common.cc
+++ b/chrome/browser/chromeos/accessibility/event_handler_common.cc
@@ -49,6 +49,7 @@ void ForwardKeyToExtension(const ui::KeyEvent& key_event,
   }
 
   const content::NativeWebKeyboardEvent web_event(key_event);
-  rvh->GetWidget()->ForwardKeyboardEvent(web_event);
+  rvh->GetWidget()->ForwardKeyboardEventWithLatencyInfo(web_event,

[dmazzoni, 2017/05/12 19:00:45]

FYI, you may want to skip tracking latency info for this one.

In this case we're capturing specific keyboard events and
forwarding them to an accessibility extension. The events
will always cancel, they'll never come back to the browser
process if not handled.

Probably not a huge deal but it seems like you may be
better off not tracking the latency for this odd use case?

[tdresser, 2017/05/12 19:09:52]

Done, thanks.

+                                                        *key_event.latency());
 }
 }  // namespace chromeos