offsetTop/offsetLeft return the wrong values for horizontal-bt/vertical-rl writing...

offsetTop/offsetLeft return the wrong values for horizontal-bt/vertical-rl writing modes
https://bugs.webkit.org/show_bug.cgi?id=68304

Reviewed by David Hyatt.

Source/WebCore:

When grabbing the x/y values of the RenderBox, we need to take writing mode
flipping into account.

Test: fast/dom/offset-position-writing-modes.html

* rendering/RenderBox.cpp:
(WebCore::RenderBox::locationIncludingFlipping):
* rendering/RenderBox.h:
(WebCore::RenderBox::yFlippedForWritingMode):
(WebCore::RenderBox::xFlippedForWritingMode):
* rendering/RenderBoxModelObject.cpp:
(WebCore::RenderBoxModelObject::offsetLeft):
(WebCore::RenderBoxModelObject::offsetTop):

LayoutTests:

* css3/flexbox/writing-modes-expected.txt:
* css3/flexbox/writing-modes.html:
* fast/dom/offset-position-writing-modes-expected.txt: Added.
* fast/dom/offset-position-writing-modes.html: Added.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@96152 268f45cc-cd09-0410-ab3c-d52691b4dbfc