We can pause the occlusion tracking before enable/disable tablet mode, and we need to reset it after the tablet mode animation finished. Think the animation that we need to track during the process is the window bounds update animation. But window bounds update animation of the process is at WindowState::SetBoundsDirectCrossFade (https://cs.chromium.org/chromium/src/ash/wm/window_state.cc?rcl=1453d9de047aedd6b084f3abdacb858109c0f576&l=735). Feel it is not doable to add an observer here to tack the completion of the animation.
After discussed with Daisy, think we may can add a class under "tablet_mode" to track the bounds of the windows. We can mark the animation as finished if the window's bounds achieves the expected bounds. Then we can reset the occlusion tracking if the animation finished.

Oshima, do you think this is doable? Or do you have any more suggestions for this? Thanks.

Before we start the CrossFadeAnimation, we call SetBoundsDirect (https://cs.chromium.org/chromium/src/ash/wm/window_state.cc?rcl=85f78938e304061d5dea7a5455ffaab5d7881adb&l=733) to set the bounds of the window. In CrossFadeAnimation what we do for animation is the transform change. Feel it might not doable to mark animation as finished based on the bounds change. Since before animation finished, the window bounds has been set to the expected bounds.

I think we may need to re-think about the tablet mode transition effect. I think too many things are going and it'd be nice if we can simplify the transition.

How about implement something simliar to overview animation, like we only animate top visible window. If it was in home screen, home screen fade outs while resumed windows are fade in.

uploaded cl:
https://chromium-review.googlesource.com/c/chromium/src/+/1332291

to pause the occlusion tracker for 500ms first.

Uploaded two recorded videos with or without the cl above. I feel I didn't see obvious change after the change.

Oshima, what do you think about this? Thanks.

Deleted: with-occlusion-tracker-pauser.webm 5.7 MB

	with-occlusion-tracker-pauser.webm 5.7 MB View Download

Deleted: no-occlusion-tracker-pauser.webm 8.5 MB

	no-occlusion-tracker-pauser.webm 8.5 MB View Download

videos were recorded on nocturne with Celeron processor.