Never position a float after it has been placed.
When a float is marked as "placed" (which happens in
LayoutBlockFlow::placeNewFloats()), it means that it has been added to a float
interval tree. It is not allowed to move a float afterwards (unless we remove
and re-insert the floats somehow, e.g. by re-laying out its containing block).
Otherwise, the interval tree may get out of sync with reality, and we may fail
to find the reference to a FloatingObject in the interval tree when deleting a
FloatingObject, so that we end up deleting the FloatingObject, but not the
reference to it in the interval tree (which will remain there, pointing to a
now dead object).
This could happen when LayoutBlockFlow::removeFloatingObjectsBelow() was called
during pagination. We sometimes need to re-lay out a line because the line or
floats next to the line get pushed to the next fragmentainer. As part of that,
we also need to get rid of the floats that we thought would sit beside the
line, and re-position them.
BUG=670927
Review-Url: https://codereview.chromium.org/2553923003
Cr-Commit-Position: refs/heads/master@{#436776}
3 files changed
