[Mac] Enable zombies for all on devchannel.
[Mac] Enable zombies for all on devchannel.

Attempt to flush out more use-after-free cases in the wild.  Right now messages to freed ObjC objects are binned by the object's address, with this change they should aggregate into a bigger bin.  Additionally, the treadmill should slightly increase the number of cases caught.

BUG=35590,24987,45676
TEST=none

Review URL: http://codereview.chromium.org/2478004

git-svn-id: http://src.chromium.org/svn/trunk/src@48838 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: f97a34ad92d3fe11cdb545970e131eaa99f946fb
meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser