ScrollingCoordinator::coordinatesScrollingForFrameView should be conditional on compo...

ScrollingCoordinator::coordinatesScrollingForFrameView should be conditional on compositing being active
https://bugs.webkit.org/show_bug.cgi?id=79126

Reviewed by Anders Carlsson.

The ScrollingCoordinator should only attempt to coordinate scrolling when compositing is active, since it's all
about manipulating GraphicsLayers. Adds a runtime check.

Also removes some stray #if ENABLE(THREADED_SCROLLING) guards that snuck into FrameView.

* page/FrameView.cpp:
(WebCore::FrameView::addFixedObject):
(WebCore::FrameView::removeFixedObject):
* page/scrolling/ScrollingCoordinator.cpp:
(WebCore::ScrollingCoordinator::coordinatesScrollingForFrameView):
(WebCore::ScrollingCoordinator::frameViewRootLayerDidChange):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@108392 268f45cc-cd09-0410-ab3c-d52691b4dbfc