Revert "Revert "[oilpan]: Make thread shutdown more robust.""

This reverts commit 3f2dc8deb5c710a408700d3b564ce1a23894d3ee.

It also adds a fix to the mac release tests seen on the bots. The issue is described in more details in http://code.google.com/p/chromium/issues/detail?id=393832.

R=ager@chromium.org, erik.corry@gmail.com, haraken@chromium.org, oilpan-reviews@chromium.org, tkent@chromium.org, zerny@chromium.org
BUG=393832,389647,391556,393744

Review URL: https://codereview.chromium.org/393823003

git-svn-id: svn://svn.chromium.org/blink/trunk@178273 bbb929c8-8fbe-4397-9dbb-9b2b20218538