Change the terminology used by rendering code when painting a given node and its children from "paintingRoot" to "subtreePaintRoot"
https://bugs.webkit.org/show_bug.cgi?id=116417

Reviewed by Sam Weinig.

PaintInfo and RenderLayer code referred to a "paintingRoot". This is only set when
FrameView::setNodeToDraw() has been called and is used to restrict painting to
some part of the subtree, but it could easily be misinterpreted, and confused with
the "rootLayer" used by RenderLayer (which is usually not the layer associated with
the paintingRoot).

Change the terminology from "paintingRoot" to "subtreePaintRoot" root to make the
purpose of this variable more obvious.

No behavior change.

* page/FrameView.cpp: Add a comment for setNodeToDraw(); in future this should
be called setSubtreePaintRoot() or something. Not done in this patch to avoid
risk; this function is exported from WebCore.
* rendering/InlineFlowBox.cpp:
(WebCore::InlineFlowBox::paint):
* rendering/PaintInfo.h:
(WebCore::PaintInfo::PaintInfo):
(WebCore::PaintInfo::updateSubtreePaintRootForChildren):
(WebCore::PaintInfo::shouldPaintWithinRoot):
* rendering/RenderBlock.cpp:
(WebCore::RenderBlock::paintContents):
* rendering/RenderBox.cpp:
(WebCore::RenderBox::paint):
* rendering/RenderLayer.cpp:
(WebCore::RenderLayer::paint):
(WebCore::RenderLayer::paintOverlayScrollbars):
(WebCore::RenderLayer::paintLayerContents):
(WebCore::RenderLayer::paintLayerByApplyingTransform):
(WebCore::RenderLayer::paintBackgroundForFragments):
(WebCore::RenderLayer::paintForegroundForFragments):
(WebCore::RenderLayer::paintForegroundForFragmentsWithPhase):
(WebCore::RenderLayer::paintOutlineForFragments):
(WebCore::RenderLayer::paintMaskForFragments):
* rendering/RenderLayer.h:
(WebCore::RenderLayer::LayerPaintingInfo::LayerPaintingInfo):
* rendering/RenderObject.cpp: Add a comment to recommend changing the name of
paintingRootRect() to refer to a subtree paint. Not done in this patch to avoid
risk; this function is exported from WebCore.
* rendering/RenderSnapshottedPlugIn.cpp:
(WebCore::RenderSnapshottedPlugIn::paint):
* rendering/RenderTable.cpp:
(WebCore::RenderTable::paintObject):
* rendering/svg/RenderSVGContainer.cpp:
(WebCore::RenderSVGContainer::paint):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@150355 268f45cc-cd09-0410-ab3c-d52691b4dbfc