Able to reproduce the issue on Windows 10 and Ubuntu 17.10 using chrome reported version #67.0.3396.99 and latest canary #69.0.3482.0. Issue is not seen in OS-mac.

Bisect Information:
=====================
Good build: 63.0.3216.0
Bad Build : 63.0.3217.0

Change Log URL: 
https://chromium.googlesource.com/chromium/src/+log/783d51fa63399dc0c7022ff06a73b2448e5632e8..96f4437916860e307ec9b8d02b098cb784430c79

From the above change log suspecting below change
Change-Id: I4866f2748dbdab800421561d8fc849d88c73280f
Reviewed-on: https://chromium-review.googlesource.com/668098

wez@ - Could you please check whether this is caused with respect to your change, if not please help us in assigning it to the right owner.

Thanks...!!

Correction: Issue is only reproducible on Win-7 and ubuntu 17.10 not on win-10.

Re #4: My CL just changes how CPU usage is reported in Chrome's Task Manager on multi-core systems. Removing the tags, since the bisect will need to be re-done.

Note that the bug report mentions high CPU usage (though it does not specify whether that is renderer, browser or system-wide CPU usage), and also low scrolling FPS.  Suggest asking reporter for more detail on the CPU measurement they were observing - issue may be an OS or driver regression.

CC'ing fsamuel@ in case they're aware of any similar reports from Viz.

I'm the reporter and this problem had happened to me and as well to others. I've built some demo page on Github and placed a link to it on Reddit and users reported the same "slowness" that I had experienced. 

I really don't think this was the case in earlier chrome versions, since that demo page existed for a year now and I wouldn't have had it online with such bad Chrome experience if I had seen it before, so I honestly think this happen after a recent Chrome change.

All I do to see this i open a Chrome browser instance (1 tab), absolutely nothing else is running in the background, and start scrolling up and down the browser is struggling and barely able to scroll.

Do you require a video of what's happening on my machine?

vsync.design@: could you capture a performance trace and attach it here. Instructions here: https://www.chromium.org/developers/how-tos/submitting-a-performance-bug

@bokan@chromium.org - 

I cannot attach it here, because even a few seconds of tracing are more than the maximum of 10MB, so here's a public link to a Google Drive dump:

https://drive.google.com/open?id=1f2PQZjqJgYw2dAfJEIFgwF7m7vvyKANP

Thank you. The trace in #8 shows the GPU process is saturated with long running tasks. Marking as untriaged so GPU team can investigate.

Interestingly, I can reproduce choppy scrolling locally with a low-DPI setup (i.e. non-composited scroller) but a trace shows that to be due to being blocked on raster. When using a high-DPI setup scrolling is smooth and a trace doesn't show much going on in the GPU process so perhaps there's something specific about OP's setup.

@bokan

Well, I'm sure this had happened to others, because I got complaints about my demo page on Github scrolling very slow, and I saw it happened to me also.

My setup is pretty normal: HP DV-6 laptop (i7 3610qm) with windows 7 SP1, with another monitor attached on HDMI, 1920x1200 & 1920x1080.

My chrome is simple, ordinary one, without almost no addons and nothing was messed around with.

chrishtr: this seems like a "we should composite background images" bug, but I couldn't find the other bug to dupe it into.

I can't reproduce this. Scrolling works just fine on Chrome 68 and 70.

Bug reporter: can you still reproduce with Chrome 68?

@chrishtr@chromium.org

Yes this happens on my machine still, with Chrome 68.0.3440.106 (Official Build) (64-bit)

You could have seen this in the trace json file I linked in the comments above no?

Maybe try asking some friends with other machines/OS mixes to try and see if this happens to them too.

I just tried again but also can't seem to repro anymore...both on 68.0.3440.106 and 70.0.3528.4 Linux, with and without --force-device-scale-factor=1 - weird.

Man, this issue is now really hurting me in another project.
A client asked to build a dashboard and the design has a linear-gradient background all over the page and it simply kills all other animations on the page, throttling them completely. I can't simply tell the client to ditch the gradient background.. I might be forced to use a real image file :/

Hope you people are working on this..