No flakiness for inspector/elements/elements-panel-limited-children.html

R=eustas
BUG=280932

Review URL: https://chromiumcodereview.appspot.com/24233005

git-svn-id: svn://svn.chromium.org/blink/trunk@158108 bbb929c8-8fbe-4397-9dbb-9b2b20218538