Add presubmit check to catch serveAsynchronousMockedRequests() usage.

BUG=366354
R=thakis@chromium.org

Review URL: https://codereview.chromium.org/271203003

git-svn-id: svn://svn.chromium.org/blink/trunk@173785 bbb929c8-8fbe-4397-9dbb-9b2b20218538