Confirming exact clank behavior from zoomed, slow-mo video capture:
- No animation of loading progress - the bar snaps to the current percentage
- Opacity animates on loading indicator over ~10 frames, or 167 ms.  So no vertical size animation, and 200 ms is likely fine for our animation.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/a6701b5b5955c9c077e799d80760413bcdeb1f88

commit a6701b5b5955c9c077e799d80760413bcdeb1f88
Author: Christopher Grant <cjgrant@chromium.org>
Date: Tue Jun 19 13:13:56 2018

VR: Animate opacity of the loading indicator

This gives the fade in/out effect on the loading progress bar that 2D UI
now has.

BUG= 853821 
R=tiborg

Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;luci.chromium.try:linux_optional_gpu_tests_rel;luci.chromium.try:linux_vr;luci.chromium.try:mac_optional_gpu_tests_rel;luci.chromium.try:win_optional_gpu_tests_rel
Change-Id: I3d07e2ea005c0fbaafb9042a257b3eac4979a4e9
Reviewed-on: https://chromium-review.googlesource.com/1104984
Commit-Queue: Christopher Grant <cjgrant@chromium.org>
Reviewed-by: Tibor Goldschwendt <tiborg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#568425}
[modify] https://crrev.com/a6701b5b5955c9c077e799d80760413bcdeb1f88/chrome/browser/vr/ui_scene_creator.cc
[modify] https://crrev.com/a6701b5b5955c9c077e799d80760413bcdeb1f88/chrome/browser/vr/ui_unittest.cc

This has been verified in Canary.

This bug requires manual review: M68 has already been promoted to the beta branch, so this requires manual review
Please contact the milestone owner if you have questions.
Owners: cmasso@(Android), kariahda@(iOS), bhthompson@(ChromeOS), abdulsyed@(Desktop)

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/f0ba179184fe316f31bb0fd31bf614453df896b9

commit f0ba179184fe316f31bb0fd31bf614453df896b9
Author: Christopher Grant <cjgrant@chromium.org>
Date: Wed Jun 20 22:40:02 2018

VR: Animate opacity of the loading indicator

This gives the fade in/out effect on the loading progress bar that 2D UI
now has.

BUG= 853821 
R=​tiborg

Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;luci.chromium.try:linux_optional_gpu_tests_rel;luci.chromium.try:linux_vr;luci.chromium.try:mac_optional_gpu_tests_rel;luci.chromium.try:win_optional_gpu_tests_rel
Change-Id: I3d07e2ea005c0fbaafb9042a257b3eac4979a4e9
Reviewed-on: https://chromium-review.googlesource.com/1104984
Commit-Queue: Christopher Grant <cjgrant@chromium.org>
Reviewed-by: Tibor Goldschwendt <tiborg@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#568425}(cherry picked from commit a6701b5b5955c9c077e799d80760413bcdeb1f88)
Reviewed-on: https://chromium-review.googlesource.com/1109138
Reviewed-by: Christopher Grant <cjgrant@chromium.org>
Cr-Commit-Position: refs/branch-heads/3440@{#468}
Cr-Branched-From: 010ddcfda246975d194964ccf20038ebbdec6084-refs/heads/master@{#561733}
[modify] https://crrev.com/f0ba179184fe316f31bb0fd31bf614453df896b9/chrome/browser/vr/ui_scene_creator.cc
[modify] https://crrev.com/f0ba179184fe316f31bb0fd31bf614453df896b9/chrome/browser/vr/ui_unittest.cc

Verified in Chrome Beta 68.0.3440.39