Try to diagnose crashes on 10.6

Canary is crashing in some strange places on just 10.6. It looks like
they are related to our (incredibly fragile) browser resize code, where
we run the message loop inside the display callback. Temporarily don't
do this on 10.6 to see if the crashes go away.

TBR=kbr@chromium.org
BUG=348328
NOTRY=True

Review URL: https://codereview.chromium.org/180273006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@254391 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 254391