Can we change the linear motion to the material curve FAST_OUT_SLOW_IN.

We may need to change the duration too, is it currently 500ms?

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/7faa5f112dd7de3208db36668cbd922589e929fc

commit 7faa5f112dd7de3208db36668cbd922589e929fc
Author: Peter Boström <pbos@chromium.org>
Date: Wed Dec 12 02:08:48 2018

Use non-linear tweens for tab-loading animation

* Uses EASE_IN_OUT for the progress bar to match the throbber.
* Uses FAST_OUT_SLOW_IN for favicon per UX request.

Bug:  chromium:912620 
Change-Id: I3ce0a376996c016904a605aa8195cc741b8e03d1
Reviewed-on: https://chromium-review.googlesource.com/c/1373016
Reviewed-by: Bret Sepulveda <bsep@chromium.org>
Commit-Queue: Peter Boström <pbos@chromium.org>
Cr-Commit-Position: refs/heads/master@{#615781}
[modify] https://crrev.com/7faa5f112dd7de3208db36668cbd922589e929fc/chrome/browser/ui/views/tabs/tab_icon.cc

The duration is currently 500ms, yes.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/4e3975ee10c53ebc415b0c58f86c5218e803078b

commit 4e3975ee10c53ebc415b0c58f86c5218e803078b
Author: Peter Boström <pbos@chromium.org>
Date: Fri Dec 14 19:49:25 2018

Tweak loading-animation speed and motion curves

These are changed to decrease the minimum time that the loading
animation can take. It's also done to make it feel snappier.

Bug:  chromium:912620 
Change-Id: If8e792cccc1f9f01bbe86909ce581bffbf1a7c35
Reviewed-on: https://chromium-review.googlesource.com/c/1377344
Commit-Queue: Avi Drissman <avi@chromium.org>
Reviewed-by: Avi Drissman <avi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#616795}
[modify] https://crrev.com/4e3975ee10c53ebc415b0c58f86c5218e803078b/chrome/browser/ui/views/tabs/tab_icon.cc
[modify] https://crrev.com/4e3975ee10c53ebc415b0c58f86c5218e803078b/ui/gfx/paint_throbber.h