Make sure to save/restore scroll positions in finishDelayUpdateScrollInfo

Make sure to save/restore scroll positions in finishDelayUpdateScrollInfo

Due to Flexbox's multi-pass layout, we may lay out children at
intermediate sizes that are very small, causing us to clamp the
scroll position at this small size. Once we lay out at the right
size, the scroll position is lost.

To avoid this problem, make finishDelayUpdateScrollInfo store
the old scroll position so it can be restored.

XXXXX THIS IS TEMPORARY XXXXX

The plan is to bake this on canary and merge this to M50 to
fix the release blocker and fix this the right way on trunk
(bug 600036), by delaying clamping of scroll offsets to after layout.

BUG=593209
Review URL: https://codereview.chromium.org/1846023003

Cr-Commit-Position: refs/heads/master@{#384772}
(cherry picked from commit ea799d37bd27d7ae346031a9332f542f7f57fd38)

Committed: https://chromium.googlesource.com/chromium/src/+/638be1f77ce930f34389fc8040ccc1b014f91dfd

[cbiesinger, 2016-04-03 01:17:54]

Description was changed from

==========
Make sure to save/restore scroll positions in finishDelayUpdateScrollInfo

Due to Flexbox's multi-pass layout, we may lay out children at
intermediate sizes that are very small, causing us to clamp the
scroll position at this small size. Once we lay out at the right
size, the scroll position is lost.

To avoid this problem, make finishDelayUpdateScrollInfo store
the old scroll position so it can be restored.

XXXXX THIS IS TEMPORARY XXXXX

The plan is to bake this on canary and merge this to M50 to
fix the release blocker and fix this the right way on trunk
(bug 600036), by delaying clamping of scroll offsets to after layout.

BUG=593209

Review URL: https://codereview.chromium.org/1846023003

Cr-Commit-Position: refs/heads/master@{#384772}
(cherry picked from commit ea799d37bd27d7ae346031a9332f542f7f57fd38)
==========

to

==========
Make sure to save/restore scroll positions in finishDelayUpdateScrollInfo

Due to Flexbox's multi-pass layout, we may lay out children at
intermediate sizes that are very small, causing us to clamp the
scroll position at this small size. Once we lay out at the right
size, the scroll position is lost.

To avoid this problem, make finishDelayUpdateScrollInfo store
the old scroll position so it can be restored.

XXXXX THIS IS TEMPORARY XXXXX

The plan is to bake this on canary and merge this to M50 to
fix the release blocker and fix this the right way on trunk
(bug 600036), by delaying clamping of scroll offsets to after layout.

BUG=593209

Review URL: https://codereview.chromium.org/1846023003

Cr-Commit-Position: refs/heads/master@{#384772}
(cherry picked from commit ea799d37bd27d7ae346031a9332f542f7f57fd38)

Committed:
https://chromium.googlesource.com/chromium/src/+/638be1f77ce930f34389fc8040cc...
==========

[cbiesinger, 2016-04-03 01:17:55]

Committed patchset #1 (id:1) manually as
638be1f77ce930f34389fc8040ccc1b014f91dfd.