Valgrind Mac: Suppress leak in MigrateBrowserPrefs.
Valgrind Mac: Suppress leak in MigrateBrowserPrefs.

BUG=71753
TEST=Mac Valgrind unit gets greener
TBR=mirandac
Review URL: http://codereview.chromium.org/6334085

git-svn-id: http://src.chromium.org/svn/trunk/src@73600 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: 336d55316336ea3de71396f64d35ceafc6cef883
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