Correct issues with fading in text when there are other leave behind items.

1) delays the start of the fade in animation for the text of the new
item until the previous leave behind item has shrunk away
2) corrects bug where the opacity of the text of the leave behind item
was not being reset
3) corrects bug where the variable tracking if an item had completed fading
in text was not being correctly reset

Fixes b/7172273 [polish] "Archived... Undo" UI jumps around when archiving multiple messages in sequence

Change-Id: Id911fdacd41892d9c0a8377c775ef7ba5d79703e
3 files changed