Turn on clang plugin checks for //url directory.

Once this sticks, the check can be removed entirely.

BUG=287029
R=thakis@chromium.org

Review URL: https://codereview.chromium.org/183763018

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@254463 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 254463