This computation did not make sense anymore since we began to put the
contents in the Row object. The fact that it worked was a coincidence.
Instead, we set rows as changed() on creation and reset that once they
have been drawn. This will allow in the future for a finer definition
of what to redraw or not.
Also update the PAINTING_ANALYSIS document
(cherry picked from commit 9e2da4a3eac83f46ab184ea8d674f84643814017)
a71610b9d7