Revert "Merge pull request #20261 from alivedise/bugzilla/1023046_2.1/app2app-transition-finetune"

This reverts commit 67b1679554cc517a5213aa2a746de26afe977eb8, reversing
changes made to f60210825f0840f95819f47a878b165019f232e9.

Conflicts:
	apps/system/test/unit/app_window_manager_test.js
Merge pull request #20972 from etiennesegonzac/bug-1023046-backout

Revert "Merge pull request #20261 from alivedise/bugzilla/1023046_2.1/ap...