[css-align] Check runtime flags for align-items 'auto' value resolution

[css-align] Check runtime flags for align-items 'auto' value resolution

The StyleAdjuster::adjustStyleForAlignment logic is optimized to avoid
resolving 'auto' values on alignment properties using its parent's
align-items default value. This way we can minimize the copy-on-write
overhead, since 'auto' is the default value of some CSS Alignment
properties.

However, align-items default value is different depending on whether the
CSS Grid Layout feature is enabled in runtime flags or not. We were not
checking out the runtime flags when applying the optimization mentioned
before, hence, when Grid is disabled, we are overwriting all the
align-self properties with 'auto' values (the default) with its parent's
align-items default value (stretch). This was verified as the root cause
of the performance regression reported in bug 642263.

This patch solves the issue by using the proper default value, depending
on the runtime flags, when evaluating whether resolving the align-self's
'auto' values or not.

BUG=642263
Review-Url: https://codereview.chromium.org/2298613004
Cr-Commit-Position: refs/heads/master@{#415795}
(cherry picked from commit bab582c0efeee11acecc6754e91d1af982044bd1)

Committed: https://chromium.googlesource.com/chromium/src/+/36d9fdb4a1f1a27447d502ef1ea457f2156154d6

[Timothy Loh, 2016-09-02 06:06:07]

Description was changed from

==========
[css-align] Check runtime flags for align-items 'auto' value resolution

The StyleAdjuster::adjustStyleForAlignment logic is optimized to avoid
resolving 'auto' values on alignment properties using its parent's
align-items default value. This way we can minimize the copy-on-write
overhead, since 'auto' is the default value of some CSS Alignment
properties.

However, align-items default value is different depending on whether the
CSS Grid Layout feature is enabled in runtime flags or not. We were not
checking out the runtime flags when applying the optimization mentioned
before, hence, when Grid is disabled, we are overwriting all the
align-self properties with 'auto' values (the default) with its parent's
align-items default value (stretch). This was verified as the root cause
of the performance regression reported in bug 642263.

This patch solves the issue by using the proper default value, depending
on the runtime flags, when evaluating whether resolving the align-self's
'auto' values or not.

BUG=642263

Review-Url: https://codereview.chromium.org/2298613004
Cr-Commit-Position: refs/heads/master@{#415795}
(cherry picked from commit bab582c0efeee11acecc6754e91d1af982044bd1)
==========

to

==========
[css-align] Check runtime flags for align-items 'auto' value resolution

The StyleAdjuster::adjustStyleForAlignment logic is optimized to avoid
resolving 'auto' values on alignment properties using its parent's
align-items default value. This way we can minimize the copy-on-write
overhead, since 'auto' is the default value of some CSS Alignment
properties.

However, align-items default value is different depending on whether the
CSS Grid Layout feature is enabled in runtime flags or not. We were not
checking out the runtime flags when applying the optimization mentioned
before, hence, when Grid is disabled, we are overwriting all the
align-self properties with 'auto' values (the default) with its parent's
align-items default value (stretch). This was verified as the root cause
of the performance regression reported in bug 642263.

This patch solves the issue by using the proper default value, depending
on the runtime flags, when evaluating whether resolving the align-self's
'auto' values or not.

BUG=642263

Review-Url: https://codereview.chromium.org/2298613004
Cr-Commit-Position: refs/heads/master@{#415795}
(cherry picked from commit bab582c0efeee11acecc6754e91d1af982044bd1)

Committed:
https://chromium.googlesource.com/chromium/src/+/36d9fdb4a1f1a27447d502ef1ea4...
==========

[Timothy Loh, 2016-09-02 06:06:11]

Committed patchset #1 (id:1) manually as
36d9fdb4a1f1a27447d502ef1ea457f2156154d6.