Merge 130549 - Deprecated flexboxes subtract scrollbar width/height twice

Merge 130549 - Deprecated flexboxes subtract scrollbar width/height twice
https://bugs.webkit.org/show_bug.cgi?id=98552

Reviewed by Tony Chang.

Source/WebCore:

This is a regression from http://trac.webkit.org/changeset/119507.
The problem is that contentHeight subtracts the scrollbar and
RenderDeprecatedFlexbox subtracts the scrollbar.

-Make it so that we only access override sizes if one has been set.
I think this makes the calling code more clear.
-If we don't have one set, grab the height/width - borderAndPadding.
-Add a FIXME to change this all back to being borderbox sizes.
There's something trick with making table padding/border work right for that
though (noted in the original patch).

Test: fast/flexbox/flexing-overflow-scroll-item.html

* rendering/RenderBox.cpp:
(WebCore::RenderBox::overrideLogicalContentWidth):
(WebCore::RenderBox::overrideLogicalContentHeight):
(WebCore::RenderBox::availableLogicalHeightUsing):
* rendering/RenderBox.h:
(RenderBox):
* rendering/RenderDeprecatedFlexibleBox.cpp:
(WebCore::contentWidthForChild):
(WebCore):
(WebCore::contentHeightForChild):
(WebCore::RenderDeprecatedFlexibleBox::layoutHorizontalBox):
(WebCore::RenderDeprecatedFlexibleBox::layoutVerticalBox):
(WebCore::RenderDeprecatedFlexibleBox::allowedChildFlex):

LayoutTests:

* fast/flexbox/flexing-overflow-scroll-item-expected.txt: Added.
* fast/flexbox/flexing-overflow-scroll-item.html: Added.

TBR=ojan@chromium.org
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=130951