This is going to be tricky for Android, because it doesn't send key events, it goes through the IME instead. The first step will be plumbing this for non-IME cases, which are essentially identical to other input latency we already report.

IME cases would likely require a fair bit of additional work.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/fcda569a9fade182b0771194e91be0ab46fb7213

commit fcda569a9fade182b0771194e91be0ab46fb7213
Author: tdresser <tdresser@chromium.org>
Date: Mon Jan 23 23:09:08 2017

Clean up LatencyInfo and RWHLatencyTracker. May break trace processing?

In preparation for landing keyboard event latency code, do some
cleanup of the existing input latency logic.

In particular, get rid of modality specific TERMINATED components.

BUG= 673731 

Review-Url: https://codereview.chromium.org/2570893003
Cr-Commit-Position: refs/heads/master@{#445532}

[modify] https://crrev.com/fcda569a9fade182b0771194e91be0ab46fb7213/content/browser/renderer_host/input/render_widget_host_latency_tracker.cc
[modify] https://crrev.com/fcda569a9fade182b0771194e91be0ab46fb7213/content/browser/renderer_host/input/render_widget_host_latency_tracker_unittest.cc
[modify] https://crrev.com/fcda569a9fade182b0771194e91be0ab46fb7213/ui/events/latency_info.cc
[modify] https://crrev.com/fcda569a9fade182b0771194e91be0ab46fb7213/ui/events/latency_info.h
[modify] https://crrev.com/fcda569a9fade182b0771194e91be0ab46fb7213/ui/events/mojo/latency_info.mojom
[modify] https://crrev.com/fcda569a9fade182b0771194e91be0ab46fb7213/ui/events/mojo/latency_info_struct_traits.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/8fef90770e83bf54f895c971ff08d5016ddabefc

commit 8fef90770e83bf54f895c971ff08d5016ddabefc
Author: tdresser <tdresser@chromium.org>
Date: Mon May 15 17:13:21 2017

Add Keyboard Latency UMA Metrics.

This doesn't correctly handle Android IME cases, or split out keyboard
scrolling from other keyboard entries.

We look specifically at events related to key presses, as most behavior is
triggered off of key press events, and key release event latency is mainly
driven by the time spent handling press related events.

Adds the following UMA metrics:
Event.Latency.QueueingTime.KeyPressDefaultPrevented
Event.Latency.QueueingTime.KeyPressDefaultAllowed
Event.Latency.BlockingTime.KeyEventDefaultPrevented
Event.Latency.BlockingTime.KeyEventDefaultAllowed

Event.Latency.Browser.KeyPressUI
Event.Latency.Browser.KeyPressAcked
Event.Latency.EndToEnd.KeyPress

BUG= 673731 
TEST=RenderWidgetHostLatencyTrackerTest.Key*
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_site_isolation

Review-Url: https://codereview.chromium.org/2756893002
Cr-Commit-Position: refs/heads/master@{#471811}

[modify] https://crrev.com/8fef90770e83bf54f895c971ff08d5016ddabefc/chrome/browser/chromeos/accessibility/event_handler_common.cc
[modify] https://crrev.com/8fef90770e83bf54f895c971ff08d5016ddabefc/chrome/browser/ui/cocoa/find_bar/find_bar_cocoa_controller.mm
[modify] https://crrev.com/8fef90770e83bf54f895c971ff08d5016ddabefc/chrome/browser/ui/views/find_bar_host.cc
[modify] https://crrev.com/8fef90770e83bf54f895c971ff08d5016ddabefc/content/browser/frame_host/render_widget_host_view_child_frame.cc
[modify] https://crrev.com/8fef90770e83bf54f895c971ff08d5016ddabefc/content/browser/frame_host/render_widget_host_view_child_frame.h
[modify] https://crrev.com/8fef90770e83bf54f895c971ff08d5016ddabefc/content/browser/renderer_host/input/render_widget_host_latency_tracker.cc
[modify] https://crrev.com/8fef90770e83bf54f895c971ff08d5016ddabefc/content/browser/renderer_host/input/render_widget_host_latency_tracker_unittest.cc
[modify] https://crrev.com/8fef90770e83bf54f895c971ff08d5016ddabefc/content/browser/renderer_host/render_widget_host_impl.cc
[modify] https://crrev.com/8fef90770e83bf54f895c971ff08d5016ddabefc/content/browser/renderer_host/render_widget_host_impl.h
[modify] https://crrev.com/8fef90770e83bf54f895c971ff08d5016ddabefc/content/browser/renderer_host/render_widget_host_unittest.cc
[modify] https://crrev.com/8fef90770e83bf54f895c971ff08d5016ddabefc/content/browser/renderer_host/render_widget_host_view_android.cc
[modify] https://crrev.com/8fef90770e83bf54f895c971ff08d5016ddabefc/content/browser/renderer_host/render_widget_host_view_aura.cc
[modify] https://crrev.com/8fef90770e83bf54f895c971ff08d5016ddabefc/content/browser/renderer_host/render_widget_host_view_aura.h
[modify] https://crrev.com/8fef90770e83bf54f895c971ff08d5016ddabefc/content/browser/renderer_host/render_widget_host_view_base.h
[modify] https://crrev.com/8fef90770e83bf54f895c971ff08d5016ddabefc/content/browser/renderer_host/render_widget_host_view_event_handler.cc
[modify] https://crrev.com/8fef90770e83bf54f895c971ff08d5016ddabefc/content/browser/renderer_host/render_widget_host_view_event_handler.h
[modify] https://crrev.com/8fef90770e83bf54f895c971ff08d5016ddabefc/content/browser/renderer_host/render_widget_host_view_mac.mm
[modify] https://crrev.com/8fef90770e83bf54f895c971ff08d5016ddabefc/content/public/browser/render_widget_host.h
[modify] https://crrev.com/8fef90770e83bf54f895c971ff08d5016ddabefc/tools/metrics/histograms/histograms.xml
[modify] https://crrev.com/8fef90770e83bf54f895c971ff08d5016ddabefc/ui/events/event.cc
[modify] https://crrev.com/8fef90770e83bf54f895c971ff08d5016ddabefc/ui/latency/latency_info.h
[modify] https://crrev.com/8fef90770e83bf54f895c971ff08d5016ddabefc/ui/latency/latency_tracker.cc
[modify] https://crrev.com/8fef90770e83bf54f895c971ff08d5016ddabefc/ui/latency/latency_tracker.h
[modify] https://crrev.com/8fef90770e83bf54f895c971ff08d5016ddabefc/ui/latency/mojo/latency_info.mojom
[modify] https://crrev.com/8fef90770e83bf54f895c971ff08d5016ddabefc/ui/latency/mojo/latency_info_struct_traits.cc