[CSS Grid Layout] Handle spanning grid items over specified grid tracks
https://bugs.webkit.org/show_bug.cgi?id=111918

Reviewed by Tony Chang.

Source/WebCore:

This change updates the containing block override logic to handle multiple
spanned tracks. This makes the multiple specified grid tracks case work and
will enable us to handle the minmax case once the computation logic has been
updated.

Test: fast/css-grid-layout/grid-item-spanning-resolution.html

* rendering/RenderGrid.cpp:
(WebCore::RenderGrid::logicalContentHeightForChild):
(WebCore::RenderGrid::layoutGridItems):
Updated these functions to use gridAreaBreadthForChild.

(WebCore::RenderGrid::gridAreaBreadthForChild):
Added this helper function to handle multiple spanned grid tracks.

* rendering/RenderGrid.h: Added the previous function.

LayoutTests:

* fast/css-grid-layout/grid-item-spanning-resolution-expected.txt:
We now pass all the tests.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@145378 268f45cc-cd09-0410-ab3c-d52691b4dbfc