fast/filesystem/workers/file-writer-write-overlapped.html crashes on release try bots.

BUG=86340
TBR=dominicc@chromium.org

Review URL: https://codereview.chromium.org/23171016

git-svn-id: svn://svn.chromium.org/blink/trunk@156278 bbb929c8-8fbe-4397-9dbb-9b2b20218538