Reland main thread position sticky implementation.

Fix the crash and reland the position sticky implementation reviewed in https://codereview.chromium.org/1308273010. TBRing reviewers on unchanged files.

BUG=231752
TEST=fast/css/sticky/*
CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel
TBR=tdresser,isherman

Review URL: https://codereview.chromium.org/1870663002

Cr-Commit-Position: refs/heads/master@{#386998}
98 files changed