UMA for PrivetTrafficDetector.
Protection against infinite rebinding.

BUG=295476
NOTRY=true

Review URL: https://chromiumcodereview.appspot.com/24387002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@224768 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 224768