During scrolling, it is very common to have a compositor frame that
needs no raster. This is the case for instance when the page is static,
and we do not need a new prepaint tile. In this case, we still add three
completion tasks to the task graph, and run them on the thread pool (on
a single thread, because they are NONCONCURRENT).
This CL runs the tasks directly if they are the only required
tasks. This saves quite a bit of overhead, and 2 thread hops (compositor
-> thread pool -> compositor) per frame. From local testing, this back
and forth often takes 800us-1ms even on a relatively simple page.
Change-Id: Ic889eddbc0d121770563fb6b0fa01f4194564972
Bug: 40419088
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6330735
Reviewed-by: Jonathan Ross <jonross@chromium.org>
Reviewed-by: Victor Miura <vmiura@chromium.org>
Commit-Queue: Benoit Lize <lizeb@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1431753}
294f5615cc