Mark two window.location shadowing tests as flaky.

BUG=381464
TBR=peter@chromium.org

Review URL: https://codereview.chromium.org/314113004

git-svn-id: svn://svn.chromium.org/blink/trunk@175604 bbb929c8-8fbe-4397-9dbb-9b2b20218538