Source/WebCore: REGRESSION: united.com has overlapping elements and is broken by flex box changes.
https://bugs.webkit.org/show_bug.cgi?id=115329
<rdar://problem/13690610>
        
The new flexbox spec says that flex-basis omitted in the flex shorthand defaults to
0 when flex-grow/shrink are set. This has undesirable behavior when objects don't
end up flexing at all, and it's something the spec is going to eventually address.
        
For now, though, to fix the regression, I'm making a targeted "hack" to deliberately
violate the spec, but to do so as minimally as possible. This hack detects if there
is infinite available space on a line, and if so, it treats a flex-basis of 0 like
auto.
        
This means that when height is constrained and set by a container, flexing will do
the right thing. Basically any time you end up actually flexing, the spec behavior
should happen. If you're just laying out at intrinsic sizes, though, and no flexing
is going to occur, we ignore a flex-basis of 0 and just use the child's normal size.
        
Note that widths don't have to be patched because the preferred logical widths
algorithm is broken right now and not checking flex-basis. If it did, we'd have seen
the same bug in the width direction.
        
This width issue is covered by https://bugs.webkit.org/show_bug.cgi?id=116117
        
Reviewed by Simon Fraser.

Added fast/flexbox/auto-height-with-flex.html

* rendering/RenderFlexibleBox.cpp:
(WebCore::RenderFlexibleBox::mainAxisContentExtent):
Make sure we return LayoutUnit::max when you have infinite free space and not
max - borderPadding.

(WebCore::RenderFlexibleBox::preferredMainAxisContentExtentForChild):
Only clear override size if it was set. Only mark for relayout if we did
an override size clear (i.e., if we were actually flexed). Add a new parameter,
hasInfiniteLineLength, that - if set - causes us to special case flex-basis:0
and treat it like flex-basis:auto.

(WebCore::RenderFlexibleBox::layoutFlexItems):
Define hasInfiniteLineLength and pass it to all the functions that need it.

(WebCore::RenderFlexibleBox::computeMainAxisPreferredSizes):
Remove the code that marks for layout and does a layout so early. This code
is moving (and changing) to preferredMainAxisContentExtentForChild.

(WebCore::RenderFlexibleBox::computeNextFlexLine):
Computes whether or not we have infinite line length now.

(WebCore::RenderFlexibleBox::freezeViolations):
(WebCore::RenderFlexibleBox::resolveFlexibleLengths):
Propagate hasInfiniteLineLength through to preferredMainAxisContentExtentForChild.

* rendering/RenderFlexibleBox.h:
(RenderFlexibleBox):
Add hasInfiniteLineLength parameter to a bunch of functions.

LayoutTests: REGRESSION (r147261): Many overlaid elements on united.com's account page
https://bugs.webkit.org/show_bug.cgi?id=116107
<rdar://problem/13690610> 

Reviewed by Simon Fraser.

* fast/flexbox/auto-height-with-flex-expected.html: Added.
* fast/flexbox/auto-height-with-flex.html: Added.



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@150087 268f45cc-cd09-0410-ab3c-d52691b4dbfc