The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/third_party/adhd/+/7006dbb24af87e0286e4abb20611e13b1b43f60d

commit 7006dbb24af87e0286e4abb20611e13b1b43f60d
Author: Yu-Hsuan Hsu <yuhsuan@chromium.org>
Date: Fri Jan 11 21:32:33 2019

CRAS: server_metrics - Log number of missed callback schedules

We record two UMA logs to check what is the frequency that the audio
thread misses callback schedules.

1. MissingCallbackFrequencyInput/Output
The number of missed callbacks for a day. It is calculated by
number of the missed callbacks / runtime of the stream.

2. MissingCallbackFirstTimeInput/Output
When the first time audio thread misses callback schedule, record how
many seconds have passed since stream started running.

BUG=chromium:918462
TEST=These UMA logs can be recorded well on peppy.

Change-Id: I588e59870d6668f3828bca0255d7703e4a42187a
Reviewed-on: https://chromium-review.googlesource.com/1392966
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Tested-by: Yu-Hsuan Hsu <yuhsuan@chromium.org>
Reviewed-by: Cheng-Yi Chiang <cychiang@chromium.org>

[modify] https://crrev.com/7006dbb24af87e0286e4abb20611e13b1b43f60d/cras/src/server/cras_rstream.c
[modify] https://crrev.com/7006dbb24af87e0286e4abb20611e13b1b43f60d/cras/src/tests/dev_stream_unittest.cc
[modify] https://crrev.com/7006dbb24af87e0286e4abb20611e13b1b43f60d/cras/src/common/cras_types.h
[modify] https://crrev.com/7006dbb24af87e0286e4abb20611e13b1b43f60d/cras/src/server/cras_server_metrics.c
[modify] https://crrev.com/7006dbb24af87e0286e4abb20611e13b1b43f60d/cras/src/server/cras_rstream.h
[modify] https://crrev.com/7006dbb24af87e0286e4abb20611e13b1b43f60d/cras/src/tests/server_metrics_unittest.cc
[modify] https://crrev.com/7006dbb24af87e0286e4abb20611e13b1b43f60d/cras/src/server/cras_server_metrics.h
[modify] https://crrev.com/7006dbb24af87e0286e4abb20611e13b1b43f60d/cras/src/server/dev_stream.c
[modify] https://crrev.com/7006dbb24af87e0286e4abb20611e13b1b43f60d/cras/src/server/audio_thread.c
[modify] https://crrev.com/7006dbb24af87e0286e4abb20611e13b1b43f60d/cras/src/tests/metrics_stub.cc
[modify] https://crrev.com/7006dbb24af87e0286e4abb20611e13b1b43f60d/cras/src/tests/cras_test_client.c
[modify] https://crrev.com/7006dbb24af87e0286e4abb20611e13b1b43f60d/cras/src/tests/rstream_unittest.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/30dd6e1152d5fd19daf365751e9e4133142195bc

commit 30dd6e1152d5fd19daf365751e9e4133142195bc
Author: Yu-Hsuan Hsu <yuhsuan@chromium.org>
Date: Thu Jan 17 16:42:29 2019

CRAS: Add histograms for missed callback schedules

The change is related to CL:1392966. Add histogram infomation in
histograms.xml to make the histogram visible on chromedashboard.

BUG=chromium:918462

(cherry picked from commit 1f8de9784eb144db7104a6c7667956a3da6c6837)

Change-Id: If073fe027dbbd448908e8e30a1576231d5d14081
Reviewed-on: https://chromium-review.googlesource.com/c/1394345
Reviewed-by: Brian White <bcwhite@chromium.org>
Commit-Queue: Yu-Hsuan Hsu <yuhsuan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#623714}
[modify] https://crrev.com/30dd6e1152d5fd19daf365751e9e4133142195bc/tools/metrics/histograms/histograms.xml