Fix issue with gc-11.html test

The test was using document.write in a setTimeout which could lead to
issues where the document.write happened too early.

This changes the test to call gc() instead of relying on setTimeout and
instead of document.write uses innerHTML

BUG=244112

Review URL: https://chromiumcodereview.appspot.com/22706005

git-svn-id: svn://svn.chromium.org/blink/trunk@155871 bbb929c8-8fbe-4397-9dbb-9b2b20218538