Table rows are incorrectly collapsed in case of hidden cells and rowspans.

When all rows in spanning cell are having only row spanning cells with empty
cell than None of the rows in spanning cell was not getting any height.

Total height of the rows in spanning cell should have at least spanning cell
height so apply spanning cell height in the last row of the spanning cells
if all rows in spanning cell are have zero height.
The total height of the rows in a spanning cell should be at least the height of
the spanning cell's itself because content should fit in the cell. This change
adds the remaining height to the last row because every row is belong to this cell only.

R=jchaffraix@chromium.org
BUG=258420,330564,341366,346150

Review URL: https://codereview.chromium.org/47923009

git-svn-id: svn://svn.chromium.org/blink/trunk@168326 bbb929c8-8fbe-4397-9dbb-9b2b20218538