Reland of Improve how the column balancer handles top margins on floats.

Reland of Improve how the column balancer handles top margins on floats. (patchset #1 id:1 of https://codereview.chromium.org/2468193002/ )

Reason for revert:
csspaint/invalidation-background-image.html was also failing (flaky) before landing this CL.

Original issue's description:
> Revert of Improve how the column balancer handles top margins on floats. (patchset #3 id:40001 of https://codereview.chromium.org/2465363003/ )
>
> Reason for revert:
> Speculative revert to fix csspaint/invalidation-background-image.html failure on "WebKit Win7 (dbg)" bot.
>
> Failed build:
> https://build.chromium.org/p/chromium.webkit/builders/WebKit%20Win7%20%28dbg%29/builds/7961
>
> Original issue's description:
> > Improve how the column balancer handles top margins on floats.
> >
> > Float margins do not collapse with column boundaries, so we should make room
> > for them after the break, if the border box of the float starts in the next
> > column.
> >
> > Let the balancer work on the margin box of the float (and the border box for
> > all other objects). For floats, we want to insert breaks before the
> > margin-before edge, not the border-before edge. This lets us remove
> > some special-code for unbreakable floats in InitialColumnHeightFinder, which
> > was the only place that previously bothered about this.
> >
> > Changed how we determine which objects to process. We used to include the
> > overflow both before and after the border box, but we really don't have to
> > bother with content preceding it, since that shouldn't undergo fragmentation
> > anyway.
> >
> > Discovered (one test regressed) that logicalHeightIncludingOverflow() also
> > included clipped overflow, which certainly wasn't the intention. This didn't
> > make much of a difference as long as the method was only called to check if we
> > could skip re-layout. But now we also use it to determine the column height.
> > Fixed it to only include visible overflow and renamed it to
> > logicalHeightWithVisibleOverflow().
> >
> > Committed: https://crrev.com/7c82da727f64121aa34aa1decf82452c37ef7a2d
> > Cr-Commit-Position: refs/heads/master@{#429245}
>
> TBR=eae@chromium.org,mstensho@opera.com
> # Skipping CQ checks because original CL landed less than 1 days ago.
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
>
> Committed: https://crrev.com/58f81484437d367285de9f0fc1fdd4034eb5c333
> Cr-Commit-Position: refs/heads/master@{#429265}

TBR=eae@chromium.org,rouslan@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Committed: https://crrev.com/df41288325ac9c6c5a8fd7bbc8bd18fa9de87ea7
Cr-Commit-Position: refs/heads/master@{#429415}

[mstensho (USE GERRIT), 2016-11-02 22:10:38]

The CQ bit was checked by mstensho@opera.com

[mstensho (USE GERRIT), 2016-11-02 22:10:38]

Created Reland of Improve how the column balancer handles top margins on floats.

[commit-bot: I haz the power, 2016-11-02 22:11:20]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-11-02 22:12:37]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-11-02 22:14:18]

Description was changed from

==========
Reland of Improve how the column balancer handles top margins on floats.
(patchset #1 id:1 of https://codereview.chromium.org/2468193002/ )

Reason for revert:
csspaint/invalidation-background-image.html was also failing (flaky) before
landing this CL.

Original issue's description:
> Revert of Improve how the column balancer handles top margins on floats.
(patchset #3 id:40001 of https://codereview.chromium.org/2465363003/ )
> 
> Reason for revert:
> Speculative revert to fix csspaint/invalidation-background-image.html failure
on "WebKit Win7 (dbg)" bot.
> 
> Failed build:
>
https://build.chromium.org/p/chromium.webkit/builders/WebKit%20Win7%20%28dbg%...
> 
> Original issue's description:
> > Improve how the column balancer handles top margins on floats.
> >
> > Float margins do not collapse with column boundaries, so we should make room
> > for them after the break, if the border box of the float starts in the next
> > column.
> >
> > Let the balancer work on the margin box of the float (and the border box for
> > all other objects). For floats, we want to insert breaks before the
> > margin-before edge, not the border-before edge. This lets us remove
> > some special-code for unbreakable floats in InitialColumnHeightFinder, which
> > was the only place that previously bothered about this.
> >
> > Changed how we determine which objects to process. We used to include the
> > overflow both before and after the border box, but we really don't have to
> > bother with content preceding it, since that shouldn't undergo fragmentation
> > anyway.
> >
> > Discovered (one test regressed) that logicalHeightIncludingOverflow() also
> > included clipped overflow, which certainly wasn't the intention. This didn't
> > make much of a difference as long as the method was only called to check if
we
> > could skip re-layout. But now we also use it to determine the column height.
> > Fixed it to only include visible overflow and renamed it to
> > logicalHeightWithVisibleOverflow().
> >
> > Committed: https://crrev.com/7c82da727f64121aa34aa1decf82452c37ef7a2d
> > Cr-Commit-Position: refs/heads/master@{#429245}
> 
> TBR=eae@chromium.org,mstensho@opera.com
> # Skipping CQ checks because original CL landed less than 1 days ago.
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
> 
> Committed: https://crrev.com/58f81484437d367285de9f0fc1fdd4034eb5c333
> Cr-Commit-Position: refs/heads/master@{#429265}

TBR=eae@chromium.org,rouslan@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
==========

to

==========
Reland of Improve how the column balancer handles top margins on floats.
(patchset #1 id:1 of https://codereview.chromium.org/2468193002/ )

Reason for revert:
csspaint/invalidation-background-image.html was also failing (flaky) before
landing this CL.

Original issue's description:
> Revert of Improve how the column balancer handles top margins on floats.
(patchset #3 id:40001 of https://codereview.chromium.org/2465363003/ )
>
> Reason for revert:
> Speculative revert to fix csspaint/invalidation-background-image.html failure
on "WebKit Win7 (dbg)" bot.
>
> Failed build:
>
https://build.chromium.org/p/chromium.webkit/builders/WebKit%20Win7%20%28dbg%...
>
> Original issue's description:
> > Improve how the column balancer handles top margins on floats.
> >
> > Float margins do not collapse with column boundaries, so we should make room
> > for them after the break, if the border box of the float starts in the next
> > column.
> >
> > Let the balancer work on the margin box of the float (and the border box for
> > all other objects). For floats, we want to insert breaks before the
> > margin-before edge, not the border-before edge. This lets us remove
> > some special-code for unbreakable floats in InitialColumnHeightFinder, which
> > was the only place that previously bothered about this.
> >
> > Changed how we determine which objects to process. We used to include the
> > overflow both before and after the border box, but we really don't have to
> > bother with content preceding it, since that shouldn't undergo fragmentation
> > anyway.
> >
> > Discovered (one test regressed) that logicalHeightIncludingOverflow() also
> > included clipped overflow, which certainly wasn't the intention. This didn't
> > make much of a difference as long as the method was only called to check if
we
> > could skip re-layout. But now we also use it to determine the column height.
> > Fixed it to only include visible overflow and renamed it to
> > logicalHeightWithVisibleOverflow().
> >
> > Committed: https://crrev.com/7c82da727f64121aa34aa1decf82452c37ef7a2d
> > Cr-Commit-Position: refs/heads/master@{#429245}
>
> TBR=eae@chromium.org,mstensho@opera.com
> # Skipping CQ checks because original CL landed less than 1 days ago.
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
>
> Committed: https://crrev.com/58f81484437d367285de9f0fc1fdd4034eb5c333
> Cr-Commit-Position: refs/heads/master@{#429265}

TBR=eae@chromium.org,rouslan@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Committed: https://crrev.com/df41288325ac9c6c5a8fd7bbc8bd18fa9de87ea7
Cr-Commit-Position: refs/heads/master@{#429415}
==========

[commit-bot: I haz the power, 2016-11-02 22:14:22]

Patchset 1 (id:??) landed as
https://crrev.com/df41288325ac9c6c5a8fd7bbc8bd18fa9de87ea7
Cr-Commit-Position: refs/heads/master@{#429415}