https://bugs.webkit.org/show_bug.cgi?id=124872

Reviewed by Brent Fulgham.

setLayerTreeStateIsFrozen is the mechanism used to ensure that
layer property changes (including new backing store) aren't committed
while e.g. the page is reconfigured for printing.

* WebProcess/WebPage/mac/RemoteLayerTreeContext.h:
* WebProcess/WebPage/mac/RemoteLayerTreeContext.mm:
(WebKit::RemoteLayerTreeContext::RemoteLayerTreeContext):
(WebKit::RemoteLayerTreeContext::flushLayers):
(WebKit::RemoteLayerTreeContext::setIsFlushingSuspended):
* WebProcess/WebPage/mac/RemoteLayerTreeDrawingArea.h:
* WebProcess/WebPage/mac/RemoteLayerTreeDrawingArea.mm:
(WebKit::RemoteLayerTreeDrawingArea::setLayerTreeStateIsFrozen):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@159956 268f45cc-cd09-0410-ab3c-d52691b4dbfc