Get rid of top level returns in layout tests.

Top level returns are not allowed by V8 any more.

Note: This CL does *not* fix the fact that the tests are completely inconsistent
wrt what to do if there are no window.eventSender or window.internals - some
print out a message, some return siletly, some alert(), some fail the test...

BUG=359194
R=jochen@chromium.org

Review URL: https://codereview.chromium.org/261853010

git-svn-id: svn://svn.chromium.org/blink/trunk@173389 bbb929c8-8fbe-4397-9dbb-9b2b20218538