The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/21cad5641d69fad06a3e94dc0d24c1e38eb8d11c

commit 21cad5641d69fad06a3e94dc0d24c1e38eb8d11c
Author: Troy Hildebrandt <thildebr@chromium.org>
Date: Thu Aug 30 20:25:59 2018

Introduce an Android CPU Frequency sampler.

Adds the ability to record CPU frequency on Android devices, viewable
in the Chrome trace viewer. Records the CPU frequency on a per-cluster
basis, meaning for a Pixel/Pixel 2 we have two separate trace counters
for CPU0-3, and CPU4-7.

The sampler is a TraceLog::EnabledStateObserver, so on Android devices
it will start and stop when tracing is enabled and disabled.

Bug:873303

Change-Id: I1702fa184f16c53f200667528bb88e96957b0e65
Reviewed-on: https://chromium-review.googlesource.com/1123029
Commit-Queue: Troy Hildebrandt <thildebr@chromium.org>
Reviewed-by: Bo <boliu@chromium.org>
Reviewed-by: Tommy Nyquist <nyquist@chromium.org>
Reviewed-by: Siddhartha S <ssid@chromium.org>
Cr-Commit-Position: refs/heads/master@{#587738}
[modify] https://crrev.com/21cad5641d69fad06a3e94dc0d24c1e38eb8d11c/base/BUILD.gn
[add] https://crrev.com/21cad5641d69fad06a3e94dc0d24c1e38eb8d11c/base/trace_event/cpufreq_monitor_android.cc
[add] https://crrev.com/21cad5641d69fad06a3e94dc0d24c1e38eb8d11c/base/trace_event/cpufreq_monitor_android.h
[add] https://crrev.com/21cad5641d69fad06a3e94dc0d24c1e38eb8d11c/base/trace_event/cpufreq_monitor_android_unittest.cc
[modify] https://crrev.com/21cad5641d69fad06a3e94dc0d24c1e38eb8d11c/components/tracing/common/trace_startup.cc
[modify] https://crrev.com/21cad5641d69fad06a3e94dc0d24c1e38eb8d11c/content/browser/browser_main_loop.cc