For example, r".*\.c" was triggering for foo.checksum.

TEST=none
BUG=none

Review URL: http://codereview.chromium.org/558026

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@37461 0039d316-1c4b-4281-b951-d872f2087c98