Remove testRunner.layoutAndPaintAsyncThen()

Now use two requestAnimationFrames instead. This reduces
dependencies of layout tests to testRunner API, making it possible
to convert them into wpt tests.

Change-Id: If9d4c82626128fb0def80eba52c85f818c2f31d2
Reviewed-on: https://chromium-review.googlesource.com/c/1395193
Commit-Queue: Xianzhu Wang <[email protected]>
Reviewed-by: Philip Rogers <[email protected]>
Reviewed-by: Antoine Labour <[email protected]>
Cr-Commit-Position: refs/heads/master@{#620925}
170 files changed