Gardening: inspector-protocol/page/enable-disable.html is flaky.

BUG=280921
TBR=rjkroege@chromium.org

Review URL: https://codereview.chromium.org/23592018

git-svn-id: svn://svn.chromium.org/blink/trunk@156892 bbb929c8-8fbe-4397-9dbb-9b2b20218538