It doesn't yet work in full-browser scenario, but allows me
to write a simple test.

TEST=Covered by browser_tests.
BUG=21541

Review URL: http://codereview.chromium.org/341050

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@30952 0039d316-1c4b-4281-b951-d872f2087c98