I'm trying to reland Kristian's crop patch https://chromium-review.googlesource.com/c/chromium/src/+/1346997
Even though this optimization, youtube fullscreen still require full 2 planes because of the transparent TILED_CONTENT quads.
I think there are 2 options.
1. youtube fullscreen fixes it.
2. skia is smart enough to notify "it's nothing" to the viz compositor.

Hi Dongseong, thanks for taking a look at this. When the CL was reverted there were a lot of regressions reported and it coincided with another CL that was reverted. It was never clear to me which CL caused the problem, but we should double check the issues that popped up last time:

  https://bugs.chromium.org/p/chromium/issues/detail?id=901055
  https://bugs.chromium.org/p/chromium/issues/detail?id=900373
  https://bugs.chromium.org/p/chromium/issues/detail?id=900744

#12 - yes, I check new patch set fixed all of the issues. As the CL mentioned, the root issue is in the following code.

  OverlayCandidateList new_candidate_list;
  if (candidate_list->size() == 1) {
    OverlayProcessor::EliminateOrCropPrimary(*quad_list, best_quad_it, &candidate_list->back(),
                                             &new_candidate_list);
  } else {
    new_candidate_list = *candidate_list;
  }

  // Check for support.
  capability_checker_->CheckOverlaySupport(&new_candidate_list);

Blackout happened because overlay strategy cropped the primary plane, no matter the overlay attempt succeed or not. See OverlayProcessor::EliminateOrCropPrimary changes |uv_rect| of candidate_list->back().

SingleOnTop or Underlay fails overlay for 2k or 4k video or something big resolution layer and vis compositor renders the primary plane with stale |uv_rect|. Users see blackout.

I see, thanks for the explanation.

Marking assigned as Dongseong appears to be investigating. If you are no longer investigating, please mark as Untriaged and we'll re-assign.