[Adding hélènepark for motion]

Motion feels much better.

Couple of notes on the bar width:
- The maximum width of the bar on the front swing to the right is almost 100%
- On the back swing to the left, the bar compresses to a width of 78%

Motion gif attached.

Deleted: refined-animation.gif 47.9 KB

	refined-animation.gif 47.9 KB View Download

I need your eyes on this, does this look better?

Deleted: different_widths.mov 150 KB

	different_widths.mov 150 KB View Download

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/1dcc7f3cd8e708b83eb3cf3886ef4a21039e6a9d

commit 1dcc7f3cd8e708b83eb3cf3886ef4a21039e6a9d
Author: Peter Boström <pbos@chromium.org>
Date: Wed Nov 21 16:00:58 2018

Update the tab-animation throbber style

Removes the round-rect end caps in favor of a rectangular throbber.

The throbber size and timings are also updated. See chromium:907435.

Bug:  chromium:907422 ,  chromium:907435 
Change-Id: I7d7a18a4d19b18361db84de829a93475a57efa44
Reviewed-on: https://chromium-review.googlesource.com/c/1346091
Reviewed-by: Edward Jung <edwardjung@chromium.org>
Reviewed-by: Avi Drissman <avi@chromium.org>
Commit-Queue: Peter Boström <pbos@chromium.org>
Cr-Commit-Position: refs/heads/master@{#610083}
[modify] https://crrev.com/1dcc7f3cd8e708b83eb3cf3886ef4a21039e6a9d/chrome/browser/ui/views/tabs/tab_icon.cc
[modify] https://crrev.com/1dcc7f3cd8e708b83eb3cf3886ef4a21039e6a9d/ui/gfx/paint_throbber.cc

I'll call this done for now, reopen if something's bad enough to fix. :)