Source/WebCore: Refined the heuristic introduced to fix <rdar://problem/10002140...

Source/WebCore: Refined the heuristic introduced to fix <rdar://problem/10002140> Text gets clipped in
multi-column layouts when overflow:auto is used.
https://bugs.webkit.org/show_bug.cgi?id=67212

Reviewed by Dave Hyatt.

Test: fast/multicol/overflow-across-columns-percent-height.html

* rendering/RenderBox.cpp:
(WebCore::percentageLogicalHeightIsResolvable): Added. This follows logic similar to the one
in computePercentageLogicalHeight() to determine whether percentage values for height properties
are resolved or treated as "auto".
(WebCore::RenderBox::hasUnsplittableScrollingOverflow): If min-height or max-height are specified
as a percentage but actually resolve to "auto", don’t let that prevent splitting.

LayoutTests: Additional test for <rdar://problem/10002140> Text gets clipped in
multi-column layouts when overflow:auto is used.
https://bugs.webkit.org/show_bug.cgi?id=67212

Reviewed by Dave Hyatt.

* fast/multicol/overflow-across-columns-percent-height.html: Added.
* platform/mac/fast/multicol/overflow-across-columns-percent-height-expected.png: Added.
* platform/mac/fast/multicol/overflow-across-columns-percent-height-expected.txt: Added.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@94253 268f45cc-cd09-0410-ab3c-d52691b4dbfc