[css-flexbox] Correctly implement contain: size on a flex item

[css-flexbox] Correctly implement contain: size on a flex item

This patch has a few changes:
- childIntrinsicLogicalHeight should not use the intrinsic content height
  for a contain: strict flex item -- if we don't have a definite size,
  we should treat its height as zero. And needToStretchChildLogicalHeight
  only returns true for an auto-height flex item.
- computeInnerFlexBaseSizeForChild does not need to trigger a layout for
  an indefinite flex basis -- those are just zero for contain: size elements.
- min-height: auto computes to 0 for contain: size
- flex items should not be layout roots even if they could otherwise be a root
  as they may need to be stretched by their parent, even if they are contain:
  strict. I have not managed to construct a testcase that fails but I don't
  see how that could be correct.

Please verify that my understanding of the containment spec is correct!

BUG=621054
R=eae@chromium.org,tabatkins@chromium.org,ojan@chromium.org,dgrogan@chromium.org

Committed: https://crrev.com/9d0095399ecfcb085e929a7d89e8db3db7a9bbf3
Cr-Commit-Position: refs/heads/master@{#410370}

[cbiesinger, 2016-08-05 21:52:49]

Also note, patch depends on https://codereview.chromium.org/2216133003/ so I
can't send it to the tryserver yet.

[eae, 2016-08-08 13:00:46]

LGTM

[cbiesinger, 2016-08-08 14:41:19]

The CQ bit was checked by cbiesinger@chromium.org

[cbiesinger, 2016-08-08 14:41:19]

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/2216903004/#ps20001
(title: "rebased")

[commit-bot: I haz the power, 2016-08-08 14:41:33]

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, 2016-08-08 16:08:30]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2016-08-08 16:10:27]

Description was changed from

==========
[css-flexbox] Correctly implement contain: size on a flex item

This patch has a few changes:
- childIntrinsicLogicalHeight should not use the intrinsic content height
  for a contain: strict flex item -- if we don't have a definite size,
  we should treat its height as zero. And needToStretchChildLogicalHeight
  only returns true for an auto-height flex item.
- computeInnerFlexBaseSizeForChild does not need to trigger a layout for
  an indefinite flex basis -- those are just zero for contain: size elements.
- min-height: auto computes to 0 for contain: size
- flex items should not be layout roots even if they could otherwise be a root
  as they may need to be stretched by their parent, even if they are contain:
  strict. I have not managed to construct a testcase that fails but I don't
  see how that could be correct.

Please verify that my understanding of the containment spec is correct!

BUG=621054
R=eae@chromium.org,tabatkins@chromium.org,ojan@chromium.org,dgrogan@chromium.org
==========

to

==========
[css-flexbox] Correctly implement contain: size on a flex item

This patch has a few changes:
- childIntrinsicLogicalHeight should not use the intrinsic content height
  for a contain: strict flex item -- if we don't have a definite size,
  we should treat its height as zero. And needToStretchChildLogicalHeight
  only returns true for an auto-height flex item.
- computeInnerFlexBaseSizeForChild does not need to trigger a layout for
  an indefinite flex basis -- those are just zero for contain: size elements.
- min-height: auto computes to 0 for contain: size
- flex items should not be layout roots even if they could otherwise be a root
  as they may need to be stretched by their parent, even if they are contain:
  strict. I have not managed to construct a testcase that fails but I don't
  see how that could be correct.

Please verify that my understanding of the containment spec is correct!

BUG=621054
R=eae@chromium.org,tabatkins@chromium.org,ojan@chromium.org,dgrogan@chromium.org

Committed: https://crrev.com/9d0095399ecfcb085e929a7d89e8db3db7a9bbf3
Cr-Commit-Position: refs/heads/master@{#410370}
==========

[commit-bot: I haz the power, 2016-08-08 16:10:28]

Patchset 2 (id:??) landed as
https://crrev.com/9d0095399ecfcb085e929a7d89e8db3db7a9bbf3
Cr-Commit-Position: refs/heads/master@{#410370}