Handle layout test crashes resulting from unexpected tombstone listings in Android.

This is a follow-up to r160926; I think other strangeness is being found
in the /data/tombstones directory, so log it and skip it to be more
robust.

TBR=peter@chromium.org, johnme@chromium.org
BUG=305040

Review URL: https://codereview.chromium.org/75683003

git-svn-id: svn://svn.chromium.org/blink/trunk@162244 bbb929c8-8fbe-4397-9dbb-9b2b20218538