Setting -webkit-column-count to auto is the same as not setting it.

Setting -webkit-column-count to auto is the same as not setting it.

In ComputedStyle, column-count is represented by two members, one integer
specifying the count, and one bool specifying whether it's auto or not. If
column-count is auto, the integer is ignored, but if the integer changes, it's
still detected as a style change (even if auto is set to true), and we'll mark
for layout for no good reason. Make sure that setting column-count to auto also
resets the integer to its initial value, to avoid this problem.

This bug was discovered while working on
https://codereview.chromium.org/1141943002/ (disable multicol when printing).
When changing from not specifying column-count to setting it to auto triggers
relayout, some printing tests started to fail (but that's really just because
the current expectation files rely on crbug.com/489615 ).

R=rune@opera.com

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=195524

[rune, 2015-05-19 09:18:15]

lgtm with nits

https://codereview.chromium.org/1145773002/diff/1/LayoutTests/fast/multicol/e...
File LayoutTests/fast/multicol/explicit-columns-auto.html (right):

https://codereview.chromium.org/1145773002/diff/1/LayoutTests/fast/multicol/e...
LayoutTests/fast/multicol/explicit-columns-auto.html:4: .explicitlyNoColumns {
-webkit-columns:auto; }
Inconsistent indentation. 2 spaces here and 4 spaces in the script below.

https://codereview.chromium.org/1145773002/diff/1/LayoutTests/fast/multicol/e...
LayoutTests/fast/multicol/explicit-columns-auto.html:12:
document.body.offsetTop;
The offsetTop forced style/layout should suffice. No need to put it in an
onload-handler?

[mstensho (USE GERRIT), 2015-05-19 09:37:17]

https://codereview.chromium.org/1145773002/diff/1/LayoutTests/fast/multicol/e...
File LayoutTests/fast/multicol/explicit-columns-auto.html (right):

https://codereview.chromium.org/1145773002/diff/1/LayoutTests/fast/multicol/e...
LayoutTests/fast/multicol/explicit-columns-auto.html:4: .explicitlyNoColumns {
-webkit-columns:auto; }
On 2015/05/19 09:18:15, rune wrote:
> Inconsistent indentation. 2 spaces here and 4 spaces in the script below.

Done.

https://codereview.chromium.org/1145773002/diff/1/LayoutTests/fast/multicol/e...
LayoutTests/fast/multicol/explicit-columns-auto.html:12:
document.body.offsetTop;
On 2015/05/19 09:18:15, rune wrote:
> The offsetTop forced style/layout should suffice. No need to put it in an
> onload-handler?

Done.

[mstensho (USE GERRIT), 2015-05-19 09:37:34]

The CQ bit was checked by mstensho@opera.com

[mstensho (USE GERRIT), 2015-05-19 09:37:34]

The patchset sent to the CQ was uploaded after l-g-t-m from rune@opera.com
Link to the patchset: https://codereview.chromium.org/1145773002/#ps20001
(title: "code review")

[commit-bot: I haz the power, 2015-05-19 09:37:50]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1145773002/20001

[commit-bot: I haz the power, 2015-05-19 11:05:04]

Committed patchset #2 (id:20001) as
https://src.chromium.org/viewvc/blink?view=rev&revision=195524