DO NOT MERGE Revert "Accept a Window as shown if it's in any transition"

This reverts commit 8ed3e4a8.

Reason for revert: Task embedding flicker b/276472426
Fix: 276472426
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:dd2ba83f7921f070ceee53a795a17c0a8127c266)
Merged-In: I81a41081ff5905cba35930f1a0de04c2000b5dfa
Change-Id: I81a41081ff5905cba35930f1a0de04c2000b5dfa