Once bug 53805 is fixed, it will be possible to make WebKit2 on Windows use DrawingAreaProxyImpl (AKA, "the new drawing area") by setting the WEBKIT2_USE_NEW_DRAWING_AREA environment variable. But there are some issues with it that make it unsuitable to turn on by default just yet. I'll file bugs for the individual issues and block this one on them.
Actually, let's use bug 53805 to track turning it on by default.