Can test some manual tests as normal tests.

There are manual tests that could be moved to normal tests. Only requires that *"test_iframe"* on *run-tests.html* is visible.

Implententación details:
 * Suggested change the visibility of the iframe only for tests that require it (forcing always visible failed some tests using IE9 in compatibility mode)
 * As a first step *manual/rendered-dimensions.html* has been moved to normal tests (to tests *Util.html* and *Util_w3c.html*)

Tested on FF, Chrome, Safari, Opera, Android and IE 6 and 9 (compatibility and not compatibility modes)