Stop media/video-controls-toggling.html from timing out.

Stop media/video-controls-toggling.html from timing out.
https://bugs.webkit.org/show_bug.cgi?id=116266

Patch by Ms2ger <Ms2ger@gmail.com> on 2017-08-21
Reviewed by Dean Jackson.

Use getComputedStyle to check the display property. Element::style only
contains properties set in the style attribute, but the display property
is set through CSS using the 'hidden' class.

* media/video-controls-toggling-expected.txt:
* media/video-controls-toggling.html:
* platform/gtk/TestExpectations:
* platform/gtk/media/video-controls-toggling-expected.txt:
  Copied from LayoutTests/media/video-controls-toggling-expected.txt.
  I'm not sure where the console message comes from, but it seems to
  be in the GTK-specific code.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@220985 268f45cc-cd09-0410-ab3c-d52691b4dbfc