Change tile tree priority on large scrolls

This CL changes the use of kNewContentForCheckerboardedScrolls to be set
more granularly per frame instead of per scroll. Currently, the feature
changes the tree priority *after* a frame has shown checkerboarding, and
keeps the priority changed until the current scroll ends.

With the changes in this CL, the priority is changed *before* the frame
is painted, and the value is reset after the first non-checkerboarded
frame. This way, we only give more time to raster to frames with large
scrolls that will need it.

Bug: 40680264
Change-Id: Ia9a0fbeb466de6ef48521c98985d5900d9fa6ead
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6655677
Reviewed-by: Robert Flack <flackr@chromium.org>
Commit-Queue: Gaston Rodriguez <gastonr@microsoft.com>
Cr-Commit-Position: refs/heads/main@{#1493650}