Telemetry: Check for branded builds on Mac OS X

R=tonyg@chromium.org, dtu@chromium.org
BUG=313317
NOTRY=true

Review URL: https://codereview.chromium.org/53143004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@231936 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 231936