[CSS3 Regions] Blocks split across regions with variable width need to size
differently in each region.
        
This patch adds the capability for blocks to have variable width and positioning
when split across regions. It is very rudimentary and so far only operates on basic
normal flow RenderBlocks. Future patches will expand the support to cover other layout
constructs like flexible boxes and tables.

Reviewed by Sam Weinig.

Added new tests in fast/regions and updated existing results.

Source/WebCore: 

* WebCore.xcodeproj/project.pbxproj:
* rendering/HitTestResult.cpp:
(WebCore::HitTestResult::HitTestResult):
(WebCore::HitTestResult::operator=):
* rendering/HitTestResult.h:
(WebCore::HitTestResult::region):
(WebCore::HitTestResult::setRegion):
The hit test result now holds the active RenderRegion so that hit testing can adjust
block widths and positions when hit testing their border boxes.

* rendering/PaintInfo.h:
(WebCore::PaintInfo::PaintInfo):
The paint info struct now holds the active RenderRegion so that painting can adjust
block widths and positions when painting borders and backgrounds and shadows.

* rendering/RenderBlock.cpp:
(WebCore::RenderBlock::layoutBlock):
If our width ever changes, we invalidate all of our cached RenderBoxRegionInfo in all
regions that we span.

(WebCore::RenderBlock::clearRenderBoxRegionInfo):
Called to clear out our cached region-specific information in all regions that we span.

(WebCore::RenderBlock::borderBoxRectInRegionAtPosition):
Returns the borderBoxRect for the region at the specified vertical offset. This rect
can be both shifted horizontally and have a different width from our original border rect.

(WebCore::RenderBlock::logicalLeftOffsetForContent):
(WebCore::RenderBlock::logicalRightOffsetForContent):
Modified to call borderBoxRectInRegionAtPosition so that lines will fit inside
the content rect of the border box rect for the specific region.

* rendering/RenderBlock.h:
(WebCore::RenderBlock::logicalRightOffsetForContent):
Modified to call logicalLeftOffsetForContent since it's cleaner.

* rendering/RenderBox.cpp:
(WebCore::RenderBox::borderBoxRectInRegion):
Called to compute the border box rect in a specific region. The result is cached in a HashMap
in the region itself so that subsequent lookups are fast.

(WebCore::RenderBox::nodeAtPoint):
Modified to use the border box rect in the active region when hit testing the backgrounds of boxes.

(WebCore::RenderBox::paintBoxDecorations):
Modified to use the border box rect in the active region when painting the backgrounds of boxes.

(WebCore::RenderBox::containingBlockLogicalWidthForContent):
(WebCore::RenderBox::containingBlockLogicalWidthForContentInRegion):
(WebCore::RenderBox::computeLogicalWidth):
(WebCore::RenderBox::computeLogicalWidthInRegion):
Helpers for computing logical widths and margins in a specific region. The result is then cached
in a HashMap in the region.

(WebCore::RenderBox::renderBoxRegionInfo):
The function for obtaining the region-specific information for a given box.

* rendering/RenderBox.h:
(WebCore::RenderBox::borderBoxRectInRegion):
New function for returning the border box rect in a given region.

* rendering/RenderBoxModelObject.cpp:
(WebCore::RenderBoxModelObject::paintFillLayerExtended):
Make sure mask painting honors the active region.

* rendering/RenderBoxRegionInfo.h: Added.
(WebCore::RenderBoxRegionInfo::RenderBoxRegionInfo):
(WebCore::RenderBoxRegionInfo::logicalLeft):
(WebCore::RenderBoxRegionInfo::logicalWidth):
(WebCore::RenderBoxRegionInfo::containingBlockChainIsShifted):
New class held by RenderRegions that caches box-specific info for a given region. This will eventually
expand to include custom styles as well, but for now it is limited to a new logical left and a new
logical width, along with a bit for optimizing accumulated shifting when painting/hit testing to avoid
too much groveling up the containing block chain.

* rendering/RenderFlowThread.cpp:
(WebCore::RenderFlowThread::RenderFlowThread):
Removed the region fitting optimization, since eventually everyone is going to care, and there's no reason
to limit it with the results now being cached.

(WebCore::RenderFlowThread::layout):
All box-specific region information is always cleared whenever the regions are invalidated.

(WebCore::RenderFlowThread::computeLogicalWidth):
Modified to set up RenderBoxRegionInfo for the flow thread in all regions.
        
(WebCore::RenderFlowThread::paintIntoRegion):
(WebCore::RenderFlowThread::hitTestRegion):
Modified to take the region instead of the region's rectangle so that painting and hit testing of the flow
thread layer tree can properly receive the active region.

(WebCore::RenderFlowThread::removeRenderBoxRegionInfo):
Helper for removing a box's information from all regions. For now it grovels through every region, so eventually
we may want to have a cache of the start/end regions for a given box somewhere.

* rendering/RenderFlowThread.h:
Removal of the region fitting stuff.

* rendering/RenderLayer.cpp:
(WebCore::RenderLayer::paint):
(WebCore::RenderLayer::paintOverlayScrollbars):
(WebCore::RenderLayer::paintLayer):
(WebCore::RenderLayer::paintList):
(WebCore::RenderLayer::paintPaginatedChildLayer):
(WebCore::RenderLayer::paintChildLayerIntoColumns):
* rendering/RenderLayer.h:
* rendering/RenderLayerBacking.cpp:
(WebCore::RenderLayerBacking::paintIntoLayer):
Modified to pass the current region down through painting functions so that it is known at paint time.

* rendering/RenderObject.cpp:
(WebCore::RenderObject::RenderObject):
Added a new bit to RenderObjects, inRenderFlowThread(), so that it is quick to determine whether or not an
object needs flow thread special casing.

(WebCore::RenderObject::enclosingRenderFlowThread):
Modified enclosingRenderFlowThread to be able to quickly return 0 if the object is not in a flow thread.

(WebCore::RenderObject::containerForRepaint):
Same.

* rendering/RenderObject.h:
(WebCore::RenderObject::setParent):
setParent now updates inRenderFlowThread() state.

(WebCore::RenderObject::inRenderFlowThread):
(WebCore::RenderObject::setInRenderFlowThread):
Adding the new bit.

* rendering/RenderObjectChildList.cpp:
(WebCore::RenderObjectChildList::removeChildNode):
Make sure when an object is removed from a RenderFlowThread that it deletes its box-specific information
in all regions.

* rendering/RenderRegion.cpp:
(WebCore::RenderRegion::~RenderRegion):
(WebCore::RenderRegion::paintReplaced):
(WebCore::RenderRegion::nodeAtPoint):
(WebCore::RenderRegion::renderBoxRegionInfo):
(WebCore::RenderRegion::setRenderBoxRegionInfo):
(WebCore::RenderRegion::removeRenderBoxRegionInfo):
(WebCore::RenderRegion::deleteAllRenderBoxRegionInfo):
(WebCore::RenderRegion::matchesRenderFlowThreadLogicalWidth):
* rendering/RenderRegion.h:
Added the new HashMap for holding box-specific region information. Also added an additional optimization to
check if a specific region matches the overall width of the RenderFlowThread. If it does, we don't need to 
cache box-specific information for that region.

* rendering/RenderReplica.cpp:
(WebCore::RenderReplica::paint):
* rendering/RenderScrollbarPart.cpp:
(WebCore::RenderScrollbarPart::paintIntoRect):
* rendering/svg/SVGImageBufferTools.cpp:
(WebCore::SVGImageBufferTools::renderSubtreeToImageBuffer):
Modified the PaintInfo construction to include the region argument. It's not optional so that callers will
have to consider it (since masks illustrated this is necessary).

LayoutTests: 

* fast/regions/percentage-margins-variable-width-regions.html: Added.
* platform/mac/fast/regions/percentage-margins-variable-width-regions-expected.png: Added.
* platform/mac/fast/regions/percentage-margins-variable-width-regions-expected.txt: Added.
* platform/mac/fast/regions/webkit-flow-double-pagination-float-push-expected.png:
* platform/mac/fast/regions/webkit-flow-float-pushed-to-last-region-expected.png:
* platform/mac/fast/regions/webkit-flow-float-unable-to-push-expected.png:
* platform/mac/fast/regions/webkit-flow-floats-inside-regions-bounds-expected.png:
* platform/mac/fast/regions/webkit-flow-inlines-dynamic-expected.png:
* platform/mac/fast/regions/webkit-flow-inlines-inside-regions-bounds-expected.png:
* platform/mac/fast/regions/webkit-flow-inlines-inside-regions-bounds-vertical-expected.png:
* platform/mac/fast/regions/webkit-flow-inlines-inside-regions-bounds-vertical-rl-expected.png:



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@96408 268f45cc-cd09-0410-ab3c-d52691b4dbfc