[GTK] [AC] Introduce AcceleratedCompositingContext to isolate different accelerated...

[GTK] [AC] Introduce AcceleratedCompositingContext to isolate different accelerated compositing implementations
https://bugs.webkit.org/show_bug.cgi?id=75519

Reviewed by Alejandro G. Castro.

Add an AcceleratedCompositingContext which will isolate all the different accelerated compositing
implementations from one another. For right now this just includes the Clutter version.

* GNUmakefile.am: Add the new files to the source list.
* WebCoreSupport/AcceleratedCompositingContext.h: Added.
* WebCoreSupport/AcceleratedCompositingContextClutter.cpp: Added. Existing
clutter AC code has moved here.
* WebCoreSupport/ChromeClientGtk.cpp:
(WebKit::ChromeClient::attachRootGraphicsLayer): Use the new AccleratedCompositingContext now
instead of calling into the WebView.
(WebKit::ChromeClient::setNeedsOneShotDrawingSynchronization):Ditto.
(WebKit::ChromeClient::scheduleCompositingLayerSync): Ditto.
* webkit/webkitwebview.cpp:
(webkit_web_view_size_allocate): Call in the ACContext.
(webkit_web_view_init): Initialize the ACContext.
* webkit/webkitwebviewprivate.h: Add the ACContext as a private member.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@104194 268f45cc-cd09-0410-ab3c-d52691b4dbfc