[Scroll Unif.] Send non-composited main thread scrolling reasons to cc

With ScrollUnification, all main-thread scrolling reasons, including
non-composited ones, are handled in cc. Without the non-composited
reasons sent to cc, cc only records kNoScrollingLayer for all
non-composited scrolling reasons, causing trouble when analyzing
metrics data.

Bug: 1413877
Change-Id: Ie2346d3ab704af41194a0815eab4114577196476
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4229099
Commit-Queue: Xianzhu Wang <wangxianzhu@chromium.org>
Reviewed-by: Steve Kobes <skobes@chromium.org>
Reviewed-by: Philip Rogers <pdr@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1104608}