Tentatively re-enable previously flaky tests.

These tests have been disabled on 2013-12-23 for being flaky.
http://crrev.com/242448 re-enabled one of the tests accidentally, and
it has been green ever since. Also, I failed to reproduce the symptoms
on ToT.

BUG=chromium:330454
TBR=thakis@chromium.org

Review URL: https://codereview.chromium.org/123833004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@243083 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 243083