Sign Native Messaging binaries on Mac

Changed do_signing.sh to use --deep when running codesign.

BUG=345967

Review URL: https://codereview.chromium.org/176113002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@252903 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 252903