Clean-up RenderTableSection::calcRowLogicalHeight

Clean-up RenderTableSection::calcRowLogicalHeight
https://bugs.webkit.org/show_bug.cgi?id=77705

Reviewed by Eric Seidel.

Refactoring / simplication of the code.

This change removes some variables that were unneeded and were
hiding what the code was really doing. Also some of the code was
split and moved down to RenderTableCell.

* rendering/RenderTableCell.cpp:
(WebCore::RenderTableCell::logicalHeightForRowSizing):
* rendering/RenderTableCell.h:
(RenderTableCell):
Added the previous helper function to calculate the cell's
adjusted logical height.

* rendering/RenderTableSection.cpp:
(WebCore::RenderTableSection::calcRowLogicalHeight):
Removed some variables, simplified the rowspan logic to be clearer
(and added a comment about how we handle rowspans).

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@108557 268f45cc-cd09-0410-ab3c-d52691b4dbfc