[CSSRegions][CSSOM] Implement Element.regionOverflow
https://bugs.webkit.org/show_bug.cgi?id=77863

Patch by Raul Hudea <rhudea@adobe.com> on 2012-02-13
Reviewed by David Hyatt.

On each layout, compute the overflowState for each region belonging to the flow thread

Tests: fast/regions/element-region-overflow-state-vertical-rl.html
       fast/regions/element-region-overflow-state.html

* dom/Element.cpp:
(WebCore::Element::webkitRegionOverflow):
(WebCore):
* dom/Element.h:
* dom/Element.idl:
* rendering/RenderBlock.cpp:
(WebCore::RenderBlock::computeOverflow):
* rendering/RenderFlowThread.cpp:
(WebCore::RenderFlowThread::computeOverflowStateForRegions):
(WebCore):
* rendering/RenderFlowThread.h:
* rendering/RenderRegion.cpp:
(WebCore::RenderRegion::RenderRegion):
* rendering/RenderRegion.h:
(RenderRegion):
(WebCore::RenderRegion::regionState):
(WebCore::RenderRegion::setRegionState):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@107652 268f45cc-cd09-0410-ab3c-d52691b4dbfc