Ash Tray: Use runtime constant string for feature pod count UMA histogram name.

BUG=964580

Change-Id: I63118cf5b8be30e7fb98d0fce62461ffac345d49
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1619046
Reviewed-by: Tetsui Ohkubo <tetsui@chromium.org>
Commit-Queue: Tim Song <tengs@chromium.org>
Cr-Commit-Position: refs/heads/master@{#661447}
1 file changed