Row spanning cell content is flowing out of the cell border if this row spanning cell comes under the boundries of other row spanning cell.

Inner row spanning cell height was not considered in table layout So Height
of the row spanning cell was not proper. Overlapping row spanning cells was
not handles.

Inner row spanning cell should handle first in the table. So we are rearranging
the list of row spanning cells so that inner row spanning cell will handled first
for spredding remaining logical height in the rows than outer row spanning cell.

List of row spanning cells is already sorted in ascending order by their
rowIndexs.
We are rearranging the row spanning cell's list and pushing inner cell before
its outer cell. Also if 2 or more row spanning cells are same but their heights
are different then pushing height-est row spanning cell before the lower height row
spanning cells.
After rearranging them, we apply the process of spreading remaining logical
height into rows.

R=jchaffraix@chromium.org
BUG=252120

Review URL: https://chromiumcodereview.appspot.com/19635004

git-svn-id: svn://svn.chromium.org/blink/trunk@155337 bbb929c8-8fbe-4397-9dbb-9b2b20218538