Additional logging in OSX mDns for investigation of attached bug.

BUG=348850

Review URL: https://codereview.chromium.org/187453004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@255350 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 255350