Scrollbars misplaced with accelerated compositing for overflow scroll
https://bugs.webkit.org/show_bug.cgi?id=108625

Reviewed by Simon Fraser.

Source/WebCore:

Scrollbars require their own layer if overflow scroll is composited,
otherwise the scrollbars would be rendered on the content layer and
not fixed to the viewport.

* rendering/RenderLayerBacking.cpp:
(WebCore::RenderLayerBacking::requiresHorizontalScrollbarLayer):
(WebCore::RenderLayerBacking::requiresVerticalScrollbarLayer):
(WebCore::RenderLayerBacking::requiresScrollCornerLayer):

LayoutTests:

Update the results for the one test that explicitly set accelerated compositing for overflow scroll,
and used to have bad results for non-chromium. The new baselines are almost identical to chomium baseline.

* platform/mac/compositing/overflow/composited-scrolling-creates-a-stacking-container-expected.txt:
* platform/qt/compositing/overflow/composited-scrolling-creates-a-stacking-container-expected.txt:


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@142140 268f45cc-cd09-0410-ab3c-d52691b4dbfc
Unreviewed, rolling out r142112.
http://trac.webkit.org/changeset/142112
https://bugs.webkit.org/show_bug.cgi?id=108990

The new test scrollingcoordinator/non-fast-scrollable-region-transformed- iframe.html crashes on Lion.

See http://test-results.appspot.com/dashboards/flakiness_dashboard.html#tests=scrollingcoordinator%2Fnon-fast-scrollable-region-transformed-iframe.html

.:

* ManualTests/remove-fixed-position-but-keep-compositing.html: Removed.

Source/WebCore:

* CMakeLists.txt:
* Target.pri:
* WebCore.pri:
* page/scrolling/ScrollingCoordinator.cpp:
(WebCore::ScrollingCoordinator::create):
* page/scrolling/coordinatedgraphics/ScrollingCoordinatorCoordinatedGraphics.cpp: Removed.
* page/scrolling/coordinatedgraphics/ScrollingCoordinatorCoordinatedGraphics.h: Removed.
* platform/graphics/texmap/coordinated/CoordinatedGraphicsLayer.cpp:
(WebCore::CoordinatedGraphicsLayer::flushCompositingState):
* platform/graphics/texmap/coordinated/CoordinatedGraphicsLayer.h:
(CoordinatedGraphicsLayerClient):
(WebCore::CoordinatedGraphicsLayer::setFixedToViewport):

Source/WebKit2:

* WebProcess/WebPage/CoordinatedGraphics/CoordinatedLayerTreeHost.cpp:
(WebKit::updateOffsetFromViewportForSelf):
(WebKit):
(WebKit::updateOffsetFromViewportForLayer):
(WebKit::CoordinatedLayerTreeHost::syncFixedLayers):
* WebProcess/WebPage/CoordinatedGraphics/CoordinatedLayerTreeHost.h:
* WebProcess/WebPage/DrawingAreaImpl.cpp:
(WebKit::DrawingAreaImpl::DrawingAreaImpl):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@142141 268f45cc-cd09-0410-ab3c-d52691b4dbfc