Build break after r149004
https://bugs.webkit.org/show_bug.cgi?id=115091

Reviewed by Csaba Osztrogonác.

* WebProcess/WebPage/gtk/LayerTreeHostGtk.cpp:
(WebKit::LayerTreeHostGtk::pageBackgroundTransparencyChanged):
(WebKit): Add dummy method for new virtual method.
* WebProcess/WebPage/gtk/LayerTreeHostGtk.h:
(LayerTreeHostGtk): Ditto.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@149017 268f45cc-cd09-0410-ab3c-d52691b4dbfc