The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/platform/tast-tests/+/dbef9976d203d2444d15549f5e8d0736286752af

commit dbef9976d203d2444d15549f5e8d0736286752af
Author: Shuhei Takahashi <nya@chromium.org>
Date: Fri Jul 20 12:30:57 2018

arc: Save logcat.

This patch will start a logcat process as soon as Android container
starts. The process will keep running and save logs to a file
until it is killed by ARC.Close().

BUG= chromium:865340 
TEST=tast -verbose run caroline-DUT arc.Boot

Change-Id: I5e3ee655e597485f2a36e880eedcb4fd7af410ae
Reviewed-on: https://chromium-review.googlesource.com/1143104
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Tested-by: Shuhei Takahashi <nya@chromium.org>
Reviewed-by: Dan Erat <derat@chromium.org>

[modify] https://crrev.com/dbef9976d203d2444d15549f5e8d0736286752af/src/chromiumos/tast/local/arc/boot_phase.go