Use ceil() when integerizing pagination struts before table rows.

Use ceil() when integerizing pagination struts before table rows.

Subpixel rendering is not supported in table parts, so everything needs to be
integers. However, instead of rounding the pagination strut down to the nearest
integer, round it up. This way we at least make sure that we manage to push all
the content over to the designated fragmentainer, rather than leaving one tiny
strip behind in the previous fragmentainer. There'll still be off-by-one
errors, but at least all the content is in the right fragmentainer.

Updated some tests to not use subpixel multicol heights, since what they
required cannot really be satisfied without adding full subpixel support to
tables.

Also added a new test that *does* use subpixel multicol height. This test
merely makes sure that nothing is left behind in the previous fragmentainer at
breaks, without worrying about the exact top position of the objects.

This problem was discovered while working on bug 487026, which is about
reducing the amount of forced re-layouts that we do for fragmentation, and it
turns out that table layout in general, and perhaps strut calculation there in
particular, tends to need more layout passes it explicitly asks for (so it
depends on other parts of the system dealing out layout passes for free). Added
body { overflow:hidden; } declarations to some tests, to reduce the number of
layout passes you get for free, i.e. make the tests more evil.

BUG=487026
Committed: https://crrev.com/435e6b536c9dd3115b7ebe9ad915487b10f0f537
Cr-Commit-Position: refs/heads/master@{#422312}

[mstensho (USE GERRIT), 2016-09-30 20:21:43]

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

[commit-bot: I haz the power, 2016-09-30 20:22:10]

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), 2016-09-30 20:22:28]

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

[eae, 2016-09-30 20:26:22]

LGTM

Please add a comment explaining why to the code.

[mstensho (USE GERRIT), 2016-09-30 21:00:17]

On 2016/09/30 20:26:22, eae wrote:
> LGTM
> 
> Please add a comment explaining why to the code.

Ohh, that was a good idea! :)

Done.

[mstensho (USE GERRIT), 2016-09-30 21:00:24]

The CQ bit was checked by mstensho@opera.com

[mstensho (USE GERRIT), 2016-09-30 21:00:25]

The patchset sent to the CQ was uploaded after l-g-t-m from eae@chromium.org
Link to the patchset: https://codereview.chromium.org/2382043003/#ps20001
(title: "Pretty good idea to explain why we round up.")

[commit-bot: I haz the power, 2016-09-30 21:01:03]

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, 2016-10-01 01:12:06]

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

[commit-bot: I haz the power, 2016-10-01 01:12:07]

Exceeded global retry quota

[mstensho (USE GERRIT), 2016-10-01 08:13:44]

The CQ bit was checked by mstensho@opera.com

[commit-bot: I haz the power, 2016-10-01 08:13:53]

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, 2016-10-01 08:17:11]

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

[commit-bot: I haz the power, 2016-10-01 08:17:12]

Failed to apply patch for
third_party/WebKit/Source/core/layout/LayoutTableSection.cpp:
While running git apply --index -3 -p1;
  error: patch failed:
third_party/WebKit/Source/core/layout/LayoutTableSection.cpp:1158
  Falling back to three-way merge...
  Applied patch to
'third_party/WebKit/Source/core/layout/LayoutTableSection.cpp' with conflicts.
  U third_party/WebKit/Source/core/layout/LayoutTableSection.cpp

Patch:       third_party/WebKit/Source/core/layout/LayoutTableSection.cpp
Index: third_party/WebKit/Source/core/layout/LayoutTableSection.cpp
diff --git a/third_party/WebKit/Source/core/layout/LayoutTableSection.cpp
b/third_party/WebKit/Source/core/layout/LayoutTableSection.cpp
index
bbe80054f0e4c599e4eb96399e5e697c07f28487..c15d383be268faf9361b96fc71341a9840ca9c85
100644
--- a/third_party/WebKit/Source/core/layout/LayoutTableSection.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutTableSection.cpp
@@ -1158,7 +1158,9 @@ int
LayoutTableSection::paginationStrutForRow(LayoutTableRow* row, LayoutUnit lo
         // completely. No point in leaving a page completely blank.
         return 0;
     }
-    return paginationStrut.toInt();
+    // Table layout parts only work on integers, so we have to round. Round up,
to make sure that no
+    // fraction ever gets left behind in the previous fragmentainer.
+    return paginationStrut.ceil();
 }
 
 void LayoutTableSection::computeOverflowFromCells()

[mstensho (USE GERRIT), 2016-10-01 10:44:18]

The CQ bit was checked by mstensho@opera.com

[mstensho (USE GERRIT), 2016-10-01 10:44:19]

The patchset sent to the CQ was uploaded after l-g-t-m from eae@chromium.org
Link to the patchset: https://codereview.chromium.org/2382043003/#ps40001
(title: "rebase master")

[commit-bot: I haz the power, 2016-10-01 10:44:24]

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, 2016-10-01 12:50:03]

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

[commit-bot: I haz the power, 2016-10-01 12:50:04]

Exceeded global retry quota

[mstensho (USE GERRIT), 2016-10-01 13:26:57]

The CQ bit was checked by mstensho@opera.com

[commit-bot: I haz the power, 2016-10-01 13:27:03]

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, 2016-10-01 13:32:28]

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

[commit-bot: I haz the power, 2016-10-01 13:32:29]

Failed to apply the patch.
On branch working_branch
Your branch is up-to-date with 'origin/refs/pending/heads/master'.
nothing to commit, working tree clean

[commit-bot: I haz the power, 2016-10-01 13:33:55]

Description was changed from

==========
Use ceil() when integerizing pagination struts before table rows.

Subpixel rendering is not supported in table parts, so everything needs to be
integers. However, instead of rounding the pagination strut down to the nearest
integer, round it up. This way we at least make sure that we manage to push all
the content over to the designated fragmentainer, rather than leaving one tiny
strip behind in the previous fragmentainer. There'll still be off-by-one
errors, but at least all the content is in the right fragmentainer.

Updated some tests to not use subpixel multicol heights, since what they
required cannot really be satisfied without adding full subpixel support to
tables.

Also added a new test that *does* use subpixel multicol height. This test
merely makes sure that nothing is left behind in the previous fragmentainer at
breaks, without worrying about the exact top position of the objects.

This problem was discovered while working on bug 487026, which is about
reducing the amount of forced re-layouts that we do for fragmentation, and it
turns out that table layout in general, and perhaps strut calculation there in
particular, tends to need more layout passes it explicitly asks for (so it
depends on other parts of the system dealing out layout passes for free). Added
body { overflow:hidden; } declarations to some tests, to reduce the number of
layout passes you get for free, i.e. make the tests more evil.

BUG=487026
==========

to

==========
Use ceil() when integerizing pagination struts before table rows.

Subpixel rendering is not supported in table parts, so everything needs to be
integers. However, instead of rounding the pagination strut down to the nearest
integer, round it up. This way we at least make sure that we manage to push all
the content over to the designated fragmentainer, rather than leaving one tiny
strip behind in the previous fragmentainer. There'll still be off-by-one
errors, but at least all the content is in the right fragmentainer.

Updated some tests to not use subpixel multicol heights, since what they
required cannot really be satisfied without adding full subpixel support to
tables.

Also added a new test that *does* use subpixel multicol height. This test
merely makes sure that nothing is left behind in the previous fragmentainer at
breaks, without worrying about the exact top position of the objects.

This problem was discovered while working on bug 487026, which is about
reducing the amount of forced re-layouts that we do for fragmentation, and it
turns out that table layout in general, and perhaps strut calculation there in
particular, tends to need more layout passes it explicitly asks for (so it
depends on other parts of the system dealing out layout passes for free). Added
body { overflow:hidden; } declarations to some tests, to reduce the number of
layout passes you get for free, i.e. make the tests more evil.

BUG=487026

Committed: https://crrev.com/435e6b536c9dd3115b7ebe9ad915487b10f0f537
Cr-Commit-Position: refs/heads/master@{#422312}
==========

[commit-bot: I haz the power, 2016-10-01 13:33:56]

Patchset 3 (id:??) landed as
https://crrev.com/435e6b536c9dd3115b7ebe9ad915487b10f0f537
Cr-Commit-Position: refs/heads/master@{#422312}