Freeze scrollbars for relayout if overflow:auto added scrollbars.

Freeze scrollbars for relayout if overflow:auto added scrollbars.

Under very specific circumstances, LayoutBlockFlow::layoutBlock will
loop infinitely in this stanza:

    while (!done)
        done = layoutBlockFlow(...);

... due to fluctuations in the existence of overflow:auto scrollbars
in descendants.  Any layout type that does multi-pass layout is
especially susceptible to this, hence this bug affecting flexbox,
and another recent bug affecting tables: crbug.com/64635.

This fix supercedes the existing fix for the table bug, and it
should fix any other variations of this bug involving multi-pass
layout and overflow:auto.

BUG=644450
R=cbiesinger@chromium.org,eae@chromium.org

Committed: https://crrev.com/906252430fe0108cf163f1fd9c2e96aa283f9cb5
Cr-Commit-Position: refs/heads/master@{#419035}

[szager1, 2016-09-15 21:48:13]

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

[commit-bot: I haz the power, 2016-09-15 21:48:47]

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

[eae, 2016-09-15 21:51:54]

LGTM
I like how well encapsulated the logic is, nicely done!

[cbiesinger1, 2016-09-15 21:59:15]

cbiesinger@google.com changed reviewers:
+ cbiesinger@google.com

[cbiesinger1, 2016-09-15 21:59:15]

lgtm

[commit-bot: I haz the power, 2016-09-15 23:21:57]

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

[commit-bot: I haz the power, 2016-09-15 23:21:58]

Dry run: This issue passed the CQ dry run.

[szager1, 2016-09-15 23:23:34]

The CQ bit was checked by szager@chromium.org

[commit-bot: I haz the power, 2016-09-15 23:23:59]

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, 2016-09-15 23:28:51]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-09-15 23:30:51]

Description was changed from

==========
Freeze scrollbars for relayout if overflow:auto added scrollbars.

Under very specific circumstances, LayoutBlockFlow::layoutBlock will
loop infinitely in this stanza:

    while (!done)
        done = layoutBlockFlow(...);

... due to fluctuations in the existence of overflow:auto scrollbars
in descendants.  Any layout type that does multi-pass layout is
especially susceptible to this, hence this bug affecting flexbox,
and another recent bug affecting tables: crbug.com/64635.

This fix supercedes the existing fix for the table bug, and it
should fix any other variations of this bug involving multi-pass
layout and overflow:auto.

BUG=644450
R=cbiesinger@chromium.org,eae@chromium.org
==========

to

==========
Freeze scrollbars for relayout if overflow:auto added scrollbars.

Under very specific circumstances, LayoutBlockFlow::layoutBlock will
loop infinitely in this stanza:

    while (!done)
        done = layoutBlockFlow(...);

... due to fluctuations in the existence of overflow:auto scrollbars
in descendants.  Any layout type that does multi-pass layout is
especially susceptible to this, hence this bug affecting flexbox,
and another recent bug affecting tables: crbug.com/64635.

This fix supercedes the existing fix for the table bug, and it
should fix any other variations of this bug involving multi-pass
layout and overflow:auto.

BUG=644450
R=cbiesinger@chromium.org,eae@chromium.org

Committed: https://crrev.com/906252430fe0108cf163f1fd9c2e96aa283f9cb5
Cr-Commit-Position: refs/heads/master@{#419035}
==========

[commit-bot: I haz the power, 2016-09-15 23:30:52]

Patchset 1 (id:??) landed as
https://crrev.com/906252430fe0108cf163f1fd9c2e96aa283f9cb5
Cr-Commit-Position: refs/heads/master@{#419035}

[mstensho (USE GERRIT), 2016-11-21 09:12:47]

mstensho@opera.com changed reviewers:
+ mstensho@opera.com

[mstensho (USE GERRIT), 2016-11-21 09:12:48]

Correct number for the table bug mentioned in the description:

https://bugs.chromium.org/p/chromium/issues/detail?id=644635