Need to reposition an out-of-flow object *before* re-paginating it.

Need to reposition an out-of-flow object *before* re-paginating it.

https://codereview.chromium.org/1343163005 removed code that was actually
needed. Instead of simply reverting the necessary parts, I rewrote them.
The old code called updateLogicalHeight() before layout, when all it wanted to
do was set the logical top. This made me a bit uneasy, because that could in
theory prevent the height change from being detected during layout() (and
LayoutBlockFlow::layoutBlockFlow() would for instance fail to set
|relayoutChildren| before calling layoutPositionedObjects()). Furthermore, it
used to check if the child establishes a writing mode root, and update the
logical *width* instead of height in that case. That's unnecessary and
potentially harmful (preventing the width change from being detected during
layout()). If the child establishes a new writing mode, it becomes opaque as
far as pagination is concerned, so no need to handle this.

BUG=544783
R=leviw@chromium.org

Committed: https://crrev.com/cd0c3a5c30540ae92f017e3c9f5309c450bf65ec
Cr-Commit-Position: refs/heads/master@{#354815}

[leviw_travelin_and_unemployed, 2015-10-19 17:05:46]

The CQ bit was checked by leviw@chromium.org

[leviw_travelin_and_unemployed, 2015-10-19 17:05:48]

lgtm

Makes sense. Thanks!

[commit-bot: I haz the power, 2015-10-19 17:06:27]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1415623002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1415623002/1

[commit-bot: I haz the power, 2015-10-19 19:08:35]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-10-19 19:09:21]

Patchset 1 (id:??) landed as
https://crrev.com/cd0c3a5c30540ae92f017e3c9f5309c450bf65ec
Cr-Commit-Position: refs/heads/master@{#354815}