Oh, sorry. I think it lost because of additional captcha screen in issue wizard.

Here is test.html and screencast.

Deleted: test.html 616 bytes

test.html 616 bytes View Download

Deleted: Screencast 2017-02-15.mp4 629 KB

	Screencast 2017-02-15.mp4 629 KB View Download

Also seen in the latest 58.0.3013.0 canary.

Bisect:
362823 (good) - 362841 (bad), 49.0.2580.0
https://chromium.googlesource.com/chromium/src/+log/4c3b7a4d..b5440a97?pretty=fuller
Suspecting r362832 ( issue 522658 ) "cc: Animate from LayerTreeHostImpl, remove Animate step from scheduler"

To reproduce, make sure smooth scrolling is enabled in chrome://flags or add it to the command line chrome --enable-smooth-scrolling

Assigning to the owner of the above CL.Tagging with current canary milestone.

I can reproduce it on linux. The scrollbar jumps between where JS is trying to put it and where the animation is trying to put it continuously until the animation stops. Then I imagine its chance which one went last.

I've build content shell at b5440a97a6472eb3bde1b1481c765a34d977bed1 and can repro there with --enable-smooth-scroll.

Reverting my CL a18e826a670891d5804c8aced282761834741e8b does make the problem stop.. in that JS stops doing anything and only the smooth scroll works.

I get the feeling the JS is supposed to interrupt the smooth scroll tho and be the authority in this case. bokan@ can you confirm?

Yes, I believe a programmatic scroll should cancel any user animations - not sure why that's not happening in this case. Dana, I'm guessing your CL changed the timing of the animation in a subtle way that breaks the cancellation? +skobes@ since he's the smooth scroll expert.

Yes the programmatic scroll is supposed to cancel the animation.

The programmatic scroll is not working before or after my CL. Before, the programatic scroll had zero effect (smooth scroll just continues cleanly). After, it does have an effect but it fights with the smooth scroll (see an alternation between the two).