Allow tool sanity suppressions to fire more than once.

This should suppress the failure on the Mac/Valgrind bot.

BUG=334074
TBR=benwells@chromium.org

Review URL: https://codereview.chromium.org/138953014

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@246838 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 246838