Fixing issue with excluded task showing when docking.

- On multi-window state changes, we should not include the front most 
  excluded task when fetching the task list.  This CL also clarifies 
  which tasks are included and excluded.

Bug: 28452689

Change-Id: Ia30eaf75382286a9d4ee5a5b11013dddf8e4ac82
7 files changed