Mac: Refactor sandbox profiles to use a common base configuration file.

      Eliminate rule duplication in our sandbox profiles by creating a new common.sb file which we include implicitly at the start of all other sandbox configuration files.

BUG=39987
TEST=Chrome on Mac should continue to render pages, all unit tests should pass.

Review URL: http://codereview.chromium.org/1656006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@44804 0039d316-1c4b-4281-b951-d872f2087c98