take padding/border on flexbox into account with direction:rtl

take padding/border on flexbox into account with direction:rtl
https://bugs.webkit.org/show_bug.cgi?id=68846

Reviewed by David Hyatt.

Source/WebCore:

Use the logicalWidth of the flexbox instead of it's availableLogicalWidth
so that we include the flexbox's border and padding.

Also, change all uses of availableLogicalWidth to contentLogicalWidth.
The former takes multi-column into account. Multi-column flexboxes don't
make any sense, so there's no point in calling availableLogicalWidth.

* rendering/RenderFlexibleBox.cpp:
(WebCore::RenderFlexibleBox::flowAwareLogicalWidth):
(WebCore::RenderFlexibleBox::flowAwareContentLogicalWidth):
(WebCore::RenderFlexibleBox::computePreferredLogicalWidth):
(WebCore::RenderFlexibleBox::runFreeSpaceAllocationAlgorithmInlineDirection):
(WebCore::RenderFlexibleBox::layoutAndPlaceChildrenInlineDirection):
* rendering/RenderFlexibleBox.h:

LayoutTests:

* css3/flexbox/writing-modes-expected.txt:
* css3/flexbox/writing-modes.html:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@96159 268f45cc-cd09-0410-ab3c-d52691b4dbfc