Only animate deletions if at least one item on screen is deleted

* This definitely addresses the first bug here (delay when deleting
  multiple items; the bug occurs if all deleted list items are off-
  screen)
* This probably addresses the second bug (downsync is delayed); this
  would happen if the UI were waiting for deletion animations to
  complete

Bug: 6268890
Bug: 6263660
Bug: 6212034
Change-Id: Ia683e35a050da8045401f7410233227afb1948ce
2 files changed