was matching everything. See
http://stackoverflow.com/questions/940822/regular-expression-syntax-for-match-nothing/940856 .

Review URL: http://codereview.chromium.org/601064

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@38965 0039d316-1c4b-4281-b951-d872f2087c98