This was originally reported here: http://stackoverflow.com/questions/35851897/google-chrome-compositor-driven-animation-affected-by-jam-in-main-thread/35856515#35856515
The developer indicates that position:absolute is what triggers the bug.

------------------

I did a bisect:

You are probably looking for a change made after 355973 (known good), but no later than 356044 (first known bad).
CHANGELOG URL:
  https://chromium.googlesource.com/chromium/src/+log/ee635cd21d022ed6737b2ea01145c0e84f28db48..8eb7906198cc0be635c92bab021b5a04c4d2c11b

suspecting https://codereview.chromium.org/1423893002 "Web Animations: Suppress compositor animations for transform on inline elements"

though also of interest is https://codereview.chromium.org/1410873003

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/1c1129d2fd8c4728671cd4f611083de6557ac5af

commit 1c1129d2fd8c4728671cd4f611083de6557ac5af
Author: dstockwell <dstockwell@chromium.org>
Date: Tue Mar 08 04:47:34 2016

Web Animations: Dont suppress compositor transform for inline-block

Transform is applied to display:inline-block/inline-transform so there's
no need to suppress compositor animations here.

BUG= 592803 

Review URL: https://codereview.chromium.org/1775743002

Cr-Commit-Position: refs/heads/master@{#379744}

[add] https://crrev.com/1c1129d2fd8c4728671cd4f611083de6557ac5af/third_party/WebKit/LayoutTests/virtual/threaded/animations/inline-block-transform.html
[modify] https://crrev.com/1c1129d2fd8c4728671cd4f611083de6557ac5af/third_party/WebKit/Source/core/animation/CompositorAnimations.cpp

Should we merge this performance regression?

Was just thinking the same thing. I'd prefer to merge to 50.

We'll give it a few days in canary first.

Your change meets the bar and is auto-approved for M50 (branch: 2661)

Please try to merge your change to M50 branch 2661 ASAP if you think it is a safe merge as we're close to M50 Beta candidate cut for next week. Thank you.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/4d73bf0ba869dd67cee7785570a5c91248a89ac3

commit 4d73bf0ba869dd67cee7785570a5c91248a89ac3
Author: Douglas Stockwell <dstockwell@chromium.org>
Date: Mon Mar 14 01:52:39 2016

Web Animations: Dont suppress compositor transform for inline-block

Transform is applied to display:inline-block/inline-transform so there's
no need to suppress compositor animations here.

BUG= 592803 

Review URL: https://codereview.chromium.org/1775743002

Cr-Commit-Position: refs/heads/master@{#379744}
(cherry picked from commit 1c1129d2fd8c4728671cd4f611083de6557ac5af)

Review URL: https://codereview.chromium.org/1789303004 .

Cr-Commit-Position: refs/branch-heads/2661@{#210}
Cr-Branched-From: ef6f6ae5e4c96622286b563658d5cd62a6cf1197-refs/heads/master@{#378081}

[add] https://crrev.com/4d73bf0ba869dd67cee7785570a5c91248a89ac3/third_party/WebKit/LayoutTests/virtual/threaded/animations/inline-block-transform.html
[modify] https://crrev.com/4d73bf0ba869dd67cee7785570a5c91248a89ac3/third_party/WebKit/Source/core/animation/CompositorAnimations.cpp

Nice! Thanks for the quick action!

Verified the merge on the latest M-50(50.0.2661.37) on Windows-7, Mac OS 10.11.3 and Linux Ubuntu 14.04. This is working as intended and animation doesn't pause & plays continuously.

Thank you!

 Issue 598679  has been merged into this issue.