REGRESSION: RenderStyle is leaked when not creating renderer for display:none

REGRESSION: RenderStyle is leaked when not creating renderer for display:none
<https://webkit.org/b/123726>

Source/WebCore:

Explicitly drop the RenderStyle reference in RenderElement::createFor
if we decide to not create any renderer.

Reviewed by Antti Koivisto.

Test: fast/css/renderstyle-leak-with-display-none.html

* rendering/RenderElement.cpp:
(WebCore::RenderElement::createFor):

LayoutTests:

Reviewed by Antti Koivisto.

* fast/css/renderstyle-leak-with-display-none-expected.txt: Added.
* fast/css/renderstyle-leak-with-display-none.html: Added.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@158570 268f45cc-cd09-0410-ab3c-d52691b4dbfc