Copied  issue chromium:820410  to issue chromium:822223

Copied  issue chromium:820410  to  issue chromium:822328 

 Issue 822544  has been merged into this issue.

I'm adding the polish for the empty state animation here. Referencing this bug in code.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/906a5ee4e6fc82f13b8ef31b44832015f8272d7c

commit 906a5ee4e6fc82f13b8ef31b44832015f8272d7c
Author: Mark Cogan <marq@google.com>
Date: Thu Mar 22 09:51:48 2018

[iOS] Tune grid dismissal when only one tab is present.

This CL tweaks the dismissal animation into the tab grid when only the
selected cell is present.

Prior to this CL, because there were no non-selected cells animating, the
animation which runs the completion block ("(4)" in the comments) would
(I think) be a no-op, so the completion block would run immediately. The
net effect is that the selected cell just jumps into place with no real
transition.

To handle this, this CL restructures the animations when there is only a
single (selected) cell to animate. Updated comments explain the new
structure.

This CL also factors out the completion block and longer animation blocks
for readability, and renumbers the animations for clarity.

Bug:  820410 
Cq-Include-Trybots: master.tryserver.chromium.mac:ios-simulator-cronet;master.tryserver.chromium.mac:ios-simulator-full-configs
Change-Id: Iaedbc131fd44b28a7fcc8b94cf5e97e46a86241c
Reviewed-on: https://chromium-review.googlesource.com/973206
Reviewed-by: edchin <edchin@chromium.org>
Commit-Queue: Mark Cogan <marq@chromium.org>
Cr-Commit-Position: refs/heads/master@{#545027}
[modify] https://crrev.com/906a5ee4e6fc82f13b8ef31b44832015f8272d7c/ios/chrome/browser/ui/tab_grid/transitions/tab_to_grid_animator.mm

Issue 836179 has been merged into this issue.

+cc martijnb@

The NextAction date has arrived: 2018-06-06

Merging animation bugs into the latest issue.