Add in row offset if self-composited.

Table cells and rows are in the same coordinate space. So to go from table offset
to row, add in the table cell's location() and subtract out the row's.

BUG=616600

Review-Url: https://codereview.chromium.org/2157243002
Cr-Commit-Position: refs/heads/master@{#406409}
5 files changed