Remove unused variable in LayerTreeHost
https://bugs.webkit.org/show_bug.cgi?id=118950

Patch by Jae Hyun Park <jae.park@company100.net> on 2013-08-31
Reviewed by Anders Carlsson.

m_waitingForUIProcess has been renamed to m_isWaitingForRenderer as of
r152183, and it is a private variable in CoordinatedLayerTreeHost. Thus,
we don't need m_waitingForUIProcess in LayerTreeHost.

* WebProcess/WebPage/LayerTreeHost.h:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@154930 268f45cc-cd09-0410-ab3c-d52691b4dbfc