Support multiple fragmentainer groups per ColumnBalancer run.

Support multiple fragmentainer groups per ColumnBalancer run.

Instead of specifying a fragmentainer group for the operation, we now specify a
column set and a flow thread portion (which may be the portion of one group or
many contiguous groups within the same column set).

The reason for this change is that when calculating space shortage in an inner
multicol container, we need to walk through all fragmentainer groups in one
operation, or we'll miss the column boundaries between the fragmentainer
groups, and only find those that lie between two columns in the same
fragmentainer group. This is especially bad if the inner multicol container
only has one column per fragmentainer group (row), since then *all* column
boundaries lie between two fragmentainer groups, and we wouldn't be able to
find any shortage at all.

BUG=594833
Committed: https://crrev.com/5b65a57f38f0260e21b8ec190d201ae2504d73e5
Cr-Commit-Position: refs/heads/master@{#388070}

[mstensho (USE GERRIT), 2016-04-15 09:05:02]

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

[leviw_travelin_and_unemployed, 2016-04-18 21:57:05]

The CQ bit was checked by leviw@chromium.org

[leviw_travelin_and_unemployed, 2016-04-18 21:57:05]

lgtm

[commit-bot: I haz the power, 2016-04-18 21:57:38]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1891783002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1891783002/1

[commit-bot: I haz the power, 2016-04-18 23:16:26]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-04-18 23:18:12]

Description was changed from

==========
Support multiple fragmentainer groups per ColumnBalancer run.

Instead of specifying a fragmentainer group for the operation, we now specify a
column set and a flow thread portion (which may be the portion of one group or
many contiguous groups within the same column set).

The reason for this change is that when calculating space shortage in an inner
multicol container, we need to walk through all fragmentainer groups in one
operation, or we'll miss the column boundaries between the fragmentainer
groups, and only find those that lie between two columns in the same
fragmentainer group. This is especially bad if the inner multicol container
only has one column per fragmentainer group (row), since then *all* column
boundaries lie between two fragmentainer groups, and we wouldn't be able to
find any shortage at all.

BUG=594833
==========

to

==========
Support multiple fragmentainer groups per ColumnBalancer run.

Instead of specifying a fragmentainer group for the operation, we now specify a
column set and a flow thread portion (which may be the portion of one group or
many contiguous groups within the same column set).

The reason for this change is that when calculating space shortage in an inner
multicol container, we need to walk through all fragmentainer groups in one
operation, or we'll miss the column boundaries between the fragmentainer
groups, and only find those that lie between two columns in the same
fragmentainer group. This is especially bad if the inner multicol container
only has one column per fragmentainer group (row), since then *all* column
boundaries lie between two fragmentainer groups, and we wouldn't be able to
find any shortage at all.

BUG=594833

Committed: https://crrev.com/5b65a57f38f0260e21b8ec190d201ae2504d73e5
Cr-Commit-Position: refs/heads/master@{#388070}
==========

[commit-bot: I haz the power, 2016-04-18 23:18:13]

Patchset 1 (id:??) landed as
https://crrev.com/5b65a57f38f0260e21b8ec190d201ae2504d73e5
Cr-Commit-Position: refs/heads/master@{#388070}