[layoutng] margin: auto support

[layoutng] margin: auto support

Add an ApplyAutoMargin function in ng_length_utils and use that from
ng_block_layout_algorithm.

I did not add it to computeMargins because not all callers should take
margin: auto into account. In particular, a child's width: auto computation
needs to treat margin: auto as zero (and, at any rate, does not have a fragment
available yet).

R=glebl@chromium.org,eae@chromium.org
BUG=635619
Committed: https://crrev.com/db9e18276e2915c4f59bb8f8f924e5a6cee3e0b7
Cr-Commit-Position: refs/heads/master@{#423680}

[cbiesinger, 2016-10-06 19:08:58]

The CQ bit was checked by cbiesinger@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-10-06 19:09:37]

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

[eae, 2016-10-06 19:11:22]

https://codereview.chromium.org/2399963002/diff/1/third_party/WebKit/Source/c...
File third_party/WebKit/Source/core/layout/ng/ng_length_utils.cc (right):

https://codereview.chromium.org/2399963002/diff/1/third_party/WebKit/Source/c...
third_party/WebKit/Source/core/layout/ng/ng_length_utils.cc:297:
margins.inline_start = margins.inline_end = available_space / 2;
This will round both of the margins down potentially loosing 1/64th.

The following seems safer:
  margins.inline_start = available_space / 2;
  margins.inline_end = available_space - margins.inline_start;

[cbiesinger, 2016-10-06 19:28:27]

https://codereview.chromium.org/2399963002/diff/1/third_party/WebKit/Source/c...
File third_party/WebKit/Source/core/layout/ng/ng_length_utils.cc (right):

https://codereview.chromium.org/2399963002/diff/1/third_party/WebKit/Source/c...
third_party/WebKit/Source/core/layout/ng/ng_length_utils.cc:297:
margins.inline_start = margins.inline_end = available_space / 2;
On 2016/10/06 19:11:22, eae wrote:
> This will round both of the margins down potentially loosing 1/64th.
> 
> The following seems safer:
>   margins.inline_start = available_space / 2;
>   margins.inline_end = available_space - margins.inline_start;

Thanks! Your suggestion is indeed what the current code does as well (in a more
convoluted way). Changed.

https://cs.chromium.org/chromium/src/third_party/WebKit/Source/core/layout/La...

[cbiesinger, 2016-10-06 19:28:32]

The CQ bit was checked by cbiesinger@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-10-06 19:29:21]

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

[eae, 2016-10-06 19:30:30]

On 2016/10/06 19:28:27, cbiesinger wrote:
>
https://codereview.chromium.org/2399963002/diff/1/third_party/WebKit/Source/c...
> File third_party/WebKit/Source/core/layout/ng/ng_length_utils.cc (right):
> 
>
https://codereview.chromium.org/2399963002/diff/1/third_party/WebKit/Source/c...
> third_party/WebKit/Source/core/layout/ng/ng_length_utils.cc:297:
> margins.inline_start = margins.inline_end = available_space / 2;
> On 2016/10/06 19:11:22, eae wrote:
> > This will round both of the margins down potentially loosing 1/64th.
> > 
> > The following seems safer:
> >   margins.inline_start = available_space / 2;
> >   margins.inline_end = available_space - margins.inline_start;
> 
> Thanks! Your suggestion is indeed what the current code does as well (in a
more
> convoluted way). Changed.

Thanks! 

LGTM

[cbiesinger, 2016-10-06 19:35:35]

The CQ bit was unchecked by cbiesinger@chromium.org

[cbiesinger, 2016-10-06 19:35:41]

The CQ bit was checked by cbiesinger@chromium.org

[commit-bot: I haz the power, 2016-10-06 19:35:49]

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

[cbiesinger, 2016-10-06 19:54:21]

The CQ bit was checked by cbiesinger@chromium.org

[cbiesinger, 2016-10-06 19:54:22]

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/2399963002/#ps40001
(title: "one more test now passes!")

[commit-bot: I haz the power, 2016-10-06 19:55:12]

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, 2016-10-06 21:15:39]

Committed patchset #3 (id:40001)

[commit-bot: I haz the power, 2016-10-06 21:17:11]

Description was changed from

==========
[layoutng] margin: auto support

Add an ApplyAutoMargin function in ng_length_utils and use that from
ng_block_layout_algorithm.

I did not add it to computeMargins because not all callers should take
margin: auto into account. In particular, a child's width: auto computation
needs to treat margin: auto as zero (and, at any rate, does not have a fragment
available yet).

R=glebl@chromium.org,eae@chromium.org
BUG=635619
==========

to

==========
[layoutng] margin: auto support

Add an ApplyAutoMargin function in ng_length_utils and use that from
ng_block_layout_algorithm.

I did not add it to computeMargins because not all callers should take
margin: auto into account. In particular, a child's width: auto computation
needs to treat margin: auto as zero (and, at any rate, does not have a fragment
available yet).

R=glebl@chromium.org,eae@chromium.org
BUG=635619

Committed: https://crrev.com/db9e18276e2915c4f59bb8f8f924e5a6cee3e0b7
Cr-Commit-Position: refs/heads/master@{#423680}
==========

[commit-bot: I haz the power, 2016-10-06 21:17:12]

Patchset 3 (id:??) landed as
https://crrev.com/db9e18276e2915c4f59bb8f8f924e5a6cee3e0b7
Cr-Commit-Position: refs/heads/master@{#423680}