Remove losing focus window list

The list was used to delay reporting focus lost to the client until the new focused window has been displayed. This is no logic is no longer needed in WM as focus is now dispatched from ID.

Bug: 151179149
Test: go/wm-smoke
Change-Id: I661a8d3ffa9c233d5f57a0037cb1317f50fa599e
2 files changed