It's the perfect place for it. It persists across builds. It would live side by side with other android specific files (adb keys). If that directory is somehow nuked, we've got a much bigger problem on our hands than simply losing device history.
See https://groups.google.com/a/google.com/forum/#!topic/chrome-infrastructure-team/R9RPhHr3HTc for motivating context.
Comment 1 by bugdroid1@chromium.org
, Jun 30 2016