Disable a flaky test.

TBR=nyquist@chromium.org
BUG=348117

Review URL: https://codereview.chromium.org/179673003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@254246 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 254246