Stay put at the top of the current page when inserting a forced break.

Stay put at the top of the current page when inserting a forced break.

If we attempt to insert a forced break, and we're already at the top of a page
or column, we should stay right there, instead of leaving an entire page or
column blank. We used to ensure this by calling nextPageLogicalTop() with
AssociateWithFormerPage.

But it was broken, because AssociateWithFormerPage could take us to a column
set preceding a column spanner that we had actually moved past. This would
confuse various parts of the machinery, and could, among other things, find
unused space in the last column preceding a spanner, and use this as a
pagination strut on an object *following* the spanner.

Remove PageBoundaryRule from nextPageLogicalTop(), and let the forced break
insertion code handle this on its own instead, and do it correctly, without
looking back at preceding columns.

BUG=647475
Committed: https://crrev.com/97ed9c5f12b724ba8db5ec1e60dd1a92cde5d05c
Cr-Commit-Position: refs/heads/master@{#420072}

[mstensho (USE GERRIT), 2016-09-21 11:51:38]

The CQ bit was checked by mstensho@opera.com to run a CQ dry run

[commit-bot: I haz the power, 2016-09-21 11:51:55]

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

[mstensho (USE GERRIT), 2016-09-21 12:57:06]

mstensho@opera.com changed reviewers:
+ eae@chromium.org

[eae, 2016-09-21 13:21:49]

Nicely clean and well tested, I like it!

LGTM

[commit-bot: I haz the power, 2016-09-21 14:51:53]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2016-09-21 14:51:54]

Dry run: Try jobs failed on following builders:
  win_chromium_rel_ng on master.tryserver.chromium.win (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.win/builders/win_chromium_rel_...)

[mstensho (USE GERRIT), 2016-09-21 14:55:16]

The CQ bit was checked by mstensho@opera.com

[commit-bot: I haz the power, 2016-09-21 14:55:35]

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, 2016-09-21 16:08:27]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-09-21 16:10:33]

Description was changed from

==========
Stay put at the top of the current page when inserting a forced break.

If we attempt to insert a forced break, and we're already at the top of a page
or column, we should stay right there, instead of leaving an entire page or
column blank. We used to ensure this by calling nextPageLogicalTop() with
AssociateWithFormerPage.

But it was broken, because AssociateWithFormerPage could take us to a column
set preceding a column spanner that we had actually moved past. This would
confuse various parts of the machinery, and could, among other things, find
unused space in the last column preceding a spanner, and use this as a
pagination strut on an object *following* the spanner.

Remove PageBoundaryRule from nextPageLogicalTop(), and let the forced break
insertion code handle this on its own instead, and do it correctly, without
looking back at preceding columns.

BUG=647475
==========

to

==========
Stay put at the top of the current page when inserting a forced break.

If we attempt to insert a forced break, and we're already at the top of a page
or column, we should stay right there, instead of leaving an entire page or
column blank. We used to ensure this by calling nextPageLogicalTop() with
AssociateWithFormerPage.

But it was broken, because AssociateWithFormerPage could take us to a column
set preceding a column spanner that we had actually moved past. This would
confuse various parts of the machinery, and could, among other things, find
unused space in the last column preceding a spanner, and use this as a
pagination strut on an object *following* the spanner.

Remove PageBoundaryRule from nextPageLogicalTop(), and let the forced break
insertion code handle this on its own instead, and do it correctly, without
looking back at preceding columns.

BUG=647475

Committed: https://crrev.com/97ed9c5f12b724ba8db5ec1e60dd1a92cde5d05c
Cr-Commit-Position: refs/heads/master@{#420072}
==========

[commit-bot: I haz the power, 2016-09-21 16:10:34]

Patchset 1 (id:??) landed as
https://crrev.com/97ed9c5f12b724ba8db5ec1e60dd1a92cde5d05c
Cr-Commit-Position: refs/heads/master@{#420072}