Remove Coordinated Graphics bits from DrawingAreaProxyImpl
https://bugs.webkit.org/show_bug.cgi?id=123382

Reviewed by Anders Carlsson.

As of r156861, Coordinated Graphics does not use DrawingAreaProxyImpl.
So, Coordinated Graphics bits should be removed from DrawingAreaProxyImpl.

* UIProcess/DrawingAreaProxyImpl.h:


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@158084 268f45cc-cd09-0410-ab3c-d52691b4dbfc