Improve multicol overflow rect calculation when column width is 0.

Improve multicol overflow rect calculation when column width is 0.

If column-gap is larger than the content box width of the multicol container,
we'll end up with zero-width column boxes (that are allowed to overflow into
neighboring gaps).

BUG=607597
Committed: https://crrev.com/46be82a9fa3fdbe05e2f8137ee61a2d3f734cab4
Cr-Commit-Position: refs/heads/master@{#391477}

[mstensho (USE GERRIT), 2016-05-03 13:03:20]

mstensho@opera.com changed reviewers:
+ eae@chromium.org, leviw@chromium.org, szager@chromium.org,
wkorman@chromium.org

[eae, 2016-05-03 13:11:28]

https://codereview.chromium.org/1927283002/diff/1/third_party/WebKit/LayoutTe...
File
third_party/WebKit/LayoutTests/fast/multicol/overflowing-columns-large-gaps.html
(right):

https://codereview.chromium.org/1927283002/diff/1/third_party/WebKit/LayoutTe...
third_party/WebKit/LayoutTests/fast/multicol/overflowing-columns-large-gaps.html:4:
<div id="container" style="overflow:auto; width:400px;"
data-expected-scroll-width="800">
Where are you getting 800 from? Two columns each 100px wide with a gap of 200px
adds up to 400 or am I missing something?

[mstensho (USE GERRIT), 2016-05-03 13:20:24]

https://codereview.chromium.org/1927283002/diff/1/third_party/WebKit/LayoutTe...
File
third_party/WebKit/LayoutTests/fast/multicol/overflowing-columns-large-gaps.html
(right):

https://codereview.chromium.org/1927283002/diff/1/third_party/WebKit/LayoutTe...
third_party/WebKit/LayoutTests/fast/multicol/overflowing-columns-large-gaps.html:4:
<div id="container" style="overflow:auto; width:400px;"
data-expected-scroll-width="800">
On 2016/05/03 13:11:28, eae wrote:
> Where are you getting 800 from? Two columns each 100px wide with a gap of
200px
> adds up to 400 or am I missing something?

Yes, the specified, computed, and used value of column-count is 2, but the
actual column-count will be larger, because the column height is only 40px. So
we'll get ceil(200/40) = 5 columns.

Used / actual column-width is 0, because the gap eats everything. Actually more
than everything. :)

So we get:
Column 0: +0px = 0px
Gap between column 0 and 1: +200px = 200px
Column 1: +0px = 200px
Gap between column 1 and 2: +200px = 400px
Column 2: +0px = 400px
Gap between column 2 and 3: +200px = 600px
Column 3: +0px = 600px
Gap between column 3 and 4: +200px = 800px
Column 4: +0px = 800px

[eae, 2016-05-03 13:27:01]

Ah, that makes sense. Thanks for explaining it.
Might warrant a comment in the test.

LGTM

[mstensho (USE GERRIT), 2016-05-04 08:36:29]

On 2016/05/03 13:27:01, eae wrote:
> Ah, that makes sense. Thanks for explaining it.
> Might warrant a comment in the test.

Done.

[mstensho (USE GERRIT), 2016-05-04 08:36:42]

The CQ bit was checked by mstensho@opera.com

[mstensho (USE GERRIT), 2016-05-04 08:36:42]

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/1927283002/#ps20001
(title: "Explain what goes on in the test.")

[commit-bot: I haz the power, 2016-05-04 08:36:48]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1927283002/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1927283002/20001

[commit-bot: I haz the power, 2016-05-04 11:01:27]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2016-05-04 11:02:25]

Description was changed from

==========
Improve multicol overflow rect calculation when column width is 0.

If column-gap is larger than the content box width of the multicol container,
we'll end up with zero-width column boxes (that are allowed to overflow into
neighboring gaps).

BUG=607597
==========

to

==========
Improve multicol overflow rect calculation when column width is 0.

If column-gap is larger than the content box width of the multicol container,
we'll end up with zero-width column boxes (that are allowed to overflow into
neighboring gaps).

BUG=607597

Committed: https://crrev.com/46be82a9fa3fdbe05e2f8137ee61a2d3f734cab4
Cr-Commit-Position: refs/heads/master@{#391477}
==========

[commit-bot: I haz the power, 2016-05-04 11:02:26]

Patchset 2 (id:??) landed as
https://crrev.com/46be82a9fa3fdbe05e2f8137ee61a2d3f734cab4
Cr-Commit-Position: refs/heads/master@{#391477}