Prevent password leakage to the suggest server by being more strict about not doing suggest when the user might have typed a username. Since we might parse this as something else (e.g. a scheme, or a hostname that's going to have a port number), the added checks are mainly for things that don't appear to be &quotusernames&quot (which were already not sent).

      BUG=51146
TEST=Unittest
Review URL: http://codereview.chromium.org/3044054

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@55496 0039d316-1c4b-4281-b951-d872f2087c98