Convert manual test added in http://trac.webkit.org/changeset/70321 to an automated...

Convert manual test added in trac.webkit.org/changeset/70321 to an automated test
https://bugs.webkit.org/show_bug.cgi?id=74729
<rdar://problem/22550195>

Reviewed by Jon Honeycutt.

.:

* ManualTests/compositing/resources/composited-subframe.html: Removed.
* ManualTests/compositing/show-composited-iframe-on-back-button.html: Removed.

LayoutTests:

* compositing/resources/composited-subframe.html: Added.
* compositing/resources/show-composited-iframe-on-back-button.css: Added.
(.container):
(.box):
* compositing/show-composited-iframe-on-back-button-expected.html: Added.
* compositing/show-composited-iframe-on-back-button.html: Added.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@189490 268f45cc-cd09-0410-ab3c-d52691b4dbfc