Revert "Merge pull request #14632 from alivedise/bugzilla/948596_v2/activity-window-size-copy"

This reverts commit 888f9df5515a47d2f5806efee77485e05e1e5416, reversing
changes made to 53b010647062b4e2637f98ac3538af1c7bfe723a.

This was backed out because of https://bugzilla.mozilla.org/show_bug.cgi?id=950136#c11