Stop unnecessary occlusion updates after unpause

This was because alpha shape was getting 'set' every commit, even though
the actual alpha shape did not change. This also prevents setting layer
filters which requires a commit on the cc side too.

Bug: 1493406
Test: CQ, local perf testing
Change-Id: Idc8c2234b0c62fe45bb37f9242a52854e279f1eb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4957498
Commit-Queue: Eliot Courtney <edcourtney@chromium.org>
Reviewed-by: Mitsuru Oshima <oshima@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1215324}