[css-flexbox] Don't over-invalidate flex items

[css-flexbox] Don't over-invalidate flex items

dirtyForLayoutFromPercentageHeightDescendants invalidates too much. We already
have code to handle this case, so remove this call. We did have a bug in
that code though -- we do need to force layout on flex items even if did not
lay them out already: such percentages are only resolvable if the flexbox has
a definite height. However, whether the flexbox height is definite may have
changed since the last layout. So, we need to relayout in either case.

The similar code in applyStretchAlignment does not have this issue because
percentages in the cross axis can be resolved independent of whether the
flexbox height itself is definite.

This is covered by an existing test; the call to
dirtyForLayoutFromPercentageHeightDescendants was previously covering this case
but is slower.

This caused a massive performance regression (many minutes to lay out a
flexbox-based website instead of a few seconds).

TEST=css3/flexbox/definite-cross-sizes.html
BUG=595361, 617792
R=dgrogan@chromium.org,eae@chromium.org

Committed: https://crrev.com/e31affc47d4167415327e54c48da086e9152ee10
Cr-Commit-Position: refs/heads/master@{#404056}

[cbiesinger, 2016-07-06 22:36:47]

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

[commit-bot: I haz the power, 2016-07-06 22:37:52]

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

[eae, 2016-07-06 23:32:58]

Nice fix, thanks for the detailed description!

LGTM

[cbiesinger, 2016-07-06 23:33:36]

The CQ bit was unchecked by cbiesinger@chromium.org

[cbiesinger, 2016-07-06 23:33:41]

The CQ bit was checked by cbiesinger@chromium.org

[commit-bot: I haz the power, 2016-07-06 23:34:38]

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, 2016-07-07 01:27:55]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2016-07-07 01:27:56]

Try jobs failed on following builders:
  win_chromium_rel_ng on master.tryserver.chromium.win (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.win/builders/win_chromium_rel_...)

[cbiesinger1, 2016-07-07 01:34:27]

The CQ bit was checked by cbiesinger@google.com

[commit-bot: I haz the power, 2016-07-07 01:34:45]

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, 2016-07-07 03:05:58]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-07-07 03:06:05]

CQ bit was unchecked.

[commit-bot: I haz the power, 2016-07-07 03:08:33]

Description was changed from

==========
[css-flexbox] Don't over-invalidate flex items

dirtyForLayoutFromPercentageHeightDescendants invalidates too much. We already
have code to handle this case, so remove this call. We did have a bug in
that code though -- we do need to force layout on flex items even if did not
lay them out already: such percentages are only resolvable if the flexbox has
a definite height. However, whether the flexbox height is definite may have
changed since the last layout. So, we need to relayout in either case.

The similar code in applyStretchAlignment does not have this issue because
percentages in the cross axis can be resolved independent of whether the
flexbox height itself is definite.

This is covered by an existing test; the call to
dirtyForLayoutFromPercentageHeightDescendants was previously covering this case
but is slower.

This caused a massive performance regression (many minutes to lay out a
flexbox-based website instead of a few seconds).

TEST=css3/flexbox/definite-cross-sizes.html
BUG=595361,617792
R=dgrogan@chromium.org,eae@chromium.org
==========

to

==========
[css-flexbox] Don't over-invalidate flex items

dirtyForLayoutFromPercentageHeightDescendants invalidates too much. We already
have code to handle this case, so remove this call. We did have a bug in
that code though -- we do need to force layout on flex items even if did not
lay them out already: such percentages are only resolvable if the flexbox has
a definite height. However, whether the flexbox height is definite may have
changed since the last layout. So, we need to relayout in either case.

The similar code in applyStretchAlignment does not have this issue because
percentages in the cross axis can be resolved independent of whether the
flexbox height itself is definite.

This is covered by an existing test; the call to
dirtyForLayoutFromPercentageHeightDescendants was previously covering this case
but is slower.

This caused a massive performance regression (many minutes to lay out a
flexbox-based website instead of a few seconds).

TEST=css3/flexbox/definite-cross-sizes.html
BUG=595361,617792
R=dgrogan@chromium.org,eae@chromium.org

Committed: https://crrev.com/e31affc47d4167415327e54c48da086e9152ee10
Cr-Commit-Position: refs/heads/master@{#404056}
==========

[commit-bot: I haz the power, 2016-07-07 03:08:35]

Patchset 1 (id:??) landed as
https://crrev.com/e31affc47d4167415327e54c48da086e9152ee10
Cr-Commit-Position: refs/heads/master@{#404056}