[//cc] Sync scrolling_contents_cull_rects for TreesInViz

Unfortunately, the tests of this functionality are all unittests that
don't actually exercise the generation of compositor frames [1].

[1] https://chromium-review.googlesource.com/c/chromium/src/+/6607188

Bug: 419083318
Change-Id: I9e01abc2bc53c0fd41d3fae7936468d907e7c0ab
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6611302
Reviewed-by: Antonio Sartori <antoniosartori@chromium.org>
Commit-Queue: Colin Blundell <blundell@chromium.org>
Reviewed-by: Victor Miura <vmiura@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1468549}