[CSS3 Regions] Fix some bugs in the computation of the logical left and width offsets
for blocks in variable width regions. Specifically, this patch addresses a minor bug
with overflow:hidden/scroll/auto block placement and with RTL directionality.

Reviewed by Sam Weinig.

Source/WebCore: 

Added five new tests in fast/regions.

* rendering/RenderBlock.cpp:
(WebCore::RenderBlock::logicalRightOffsetForContent):
Avoid a double fetch of the border box in a given region by not calling
logicalLeftOffsetForContent. No correctness change here. It's just cleaner.

* rendering/RenderBox.cpp:
(WebCore::RenderBox::borderBoxRectInRegion):
Change the shifted optimization to be cached for "self" rather than for "containing block".
Rework the adjustment loop to handle changes in directionality and to fix correctness
issues with RTL.

(WebCore::RenderBox::containingBlockLogicalWidthForContentInRegion):
Don't double adjust if an object uses line width as the containing block width. In that
case we already computed the line width in the region, so we don't need to apply any
additional fixup.

(WebCore::RenderBox::renderBoxRegionInfo):
* rendering/RenderBoxRegionInfo.h:
(WebCore::RenderBoxRegionInfo::RenderBoxRegionInfo):
(WebCore::RenderBoxRegionInfo::isShifted):
Changed the shifted code to be on self rather than on containing block.

* rendering/RenderFlowThread.cpp:
(WebCore::RenderFlowThread::layout):
Refactor the layout code for RenderFlowThread to properly set up region rects assuming
right alignment in RTL code. This change forces us to compute our maximum logical width
first before looping through the regions again to set their content rects.

LayoutTests: 

* fast/regions/overflow-in-variable-width-regions.html: Added.
* fast/regions/overflow-rtl-in-variable-width-regions.html: Added.
* fast/regions/percentage-margins-mixed-ltr-dominant-regions.html: Added.
* fast/regions/percentage-margins-mixed-rtl-dominant-regions.html: Added.
* fast/regions/percentage-margins-rtl-variable-width-regions.html: Added.
* platform/mac/fast/regions/overflow-in-variable-width-regions-expected.png: Added.
* platform/mac/fast/regions/overflow-in-variable-width-regions-expected.txt: Added.
* platform/mac/fast/regions/overflow-rtl-in-variable-width-regions-expected.png: Added.
* platform/mac/fast/regions/overflow-rtl-in-variable-width-regions-expected.txt: Added.
* platform/mac/fast/regions/percentage-margins-mixed-ltr-dominant-regions-expected.png: Added.
* platform/mac/fast/regions/percentage-margins-mixed-ltr-dominant-regions-expected.txt: Added.
* platform/mac/fast/regions/percentage-margins-mixed-rtl-dominant-regions-expected.png: Added.
* platform/mac/fast/regions/percentage-margins-mixed-rtl-dominant-regions-expected.txt: Added.
* platform/mac/fast/regions/percentage-margins-rtl-variable-width-regions-expected.png: Added.
* platform/mac/fast/regions/percentage-margins-rtl-variable-width-regions-expected.txt: Added.



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@96423 268f45cc-cd09-0410-ab3c-d52691b4dbfc