I just remembered, sometimes the mouse will stutter when the hiccup occurs. So maybe it's a system call that's hanging?

Thanks for the report! I do see these hangs in the trace, and it appears to be due to an extension. However, I can't quite tell from the trace which extension is causing the issue.

Could you try to play video in incognito mode to see if this fixes the issue? If so, could you (in a non-incognito window) go through about:extensions try disabling the extensions one-by-one to see which one seems to be causing the issue?

@Devlin see the trace, the time blocks are due to ExtensionHostMsg_Request. Is my diagnosis correct? Are there any other trace categories that would help here?

Thanks for the quick reply! I tried in incognito mode (and verified that no extensions are allowed), but the problem persists. Here's another trace.

I do have a few apps that seem to still show up (Hangouts, for example). Let me know if I should disable them and try again.

Deleted: trace_withoutExtensions.json.gz 4.2 MB

trace_withoutExtensions.json.gz 4.2 MB Download

I took a look at the trace myself, not really knowing what I'm looking for. I think the CSS Animation events correlate roughly with the hiccups.

Thanks for that! I still see activity coming from that same extensions function. It would be good to try incognito with no extensions enabled. You can do that by:

1) going to about:extensions
2) for each extension, click Details and then uncheck "Allow in incognito"

Huh ok, it appears to be from the Hangouts App (not extension, this one: https://chrome.google.com/webstore/detail/google-hangouts/knipolnnllmklapflnccelgolnpehhpl). Any idea why that's interfering so heavily?

Thanks for the help tracking it down!

Got it, thanks for the investigation. Let me follow-up with the Hangouts team and see what I can learn.

> @Devlin see the trace, the time blocks are due to ExtensionHostMsg_Request. Is my diagnosis correct? Are there any other trace categories that would help here?

Unfortunately, my tracing knowledge is all-but nonexistent.  However, ExtensionHostMsg_Request corresponds to, pretty much, any extension API call.  So the fact that we see it taking hundreds of ms implies that there was a very expensive extension API call being executed in that block (or many smaller ones - but I think those would show up as separate blocks?).  If we could see the IPC parameters, we could tell which API call it was, but otherwise we'd need to add some custom logs or figure it out some other way.

If this proves hard to reproduce, let me know - I'm happy to do more troubleshooting.

Quick update - it appears that the problem also exists with the extension (https://chrome.google.com/webstore/detail/google-hangouts/nckgahadagoaajjgafhacjanaoiihapd)

Unable to reproduce the issue on reported chrome version 66.0.3359.117 using Windows 10 with the below mentioned steps.

Steps:
-----------
1. Launched chrome
2. Navigated to given URL> ""(https://chrome.google.com/webstore/detail/google-hangouts/nckgahadagoaajjgafhacjanaoiihapd)""
3. Added hangout extension to chrome
3. Observed there is no hiccup in video.
4. Disabled/Enabled the hardware accelerate and started from step one.
5. Observed there is no hiccup in video.

As we are unable to reproduce the issue from our end. Can you verify this issue with fresh profile that is not having any extensions and apps or reset all the flags. Let us know whether issue still persists.

Thanks! 

I just replicated it on 67.0.3396.30 (I've updated since the initial report).
Steps taken:
1. Create new Windows account
2. Open Chrome
3. Sign in to alternate Google account with no extensions synced
4. Install Hangouts extension (https://chrome.google.com/webstore/detail/google-hangouts/nckgahadagoaajjgafhacjanaoiihapd?hl=en)
5. Hangouts opens automatically, using my alt Google account
6. Open Youtube, specifically https://www.youtube.com/watch?v=8h--kFui1JA
7. Enable stats for nerds
8. Watch dropped frames (first number) increase by 2 every 10-20 seconds, with noticeable hiccup in video.

I confirmed that all flags were on default, as were all settings (i.e. hardware acceleration is on, by default).

I'm running an RX 480 video card with 4 monitors, in case that's relevant. I can provide other hardware specs if desired, but there's nothing crazy attached.

Thank you for providing more feedback. Adding the requester to the cc list.

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

Additionally, here's another trace from the new profile.

Deleted: trace_newProfile.json.gz 6.7 MB

trace_newProfile.json.gz 6.7 MB Download

Note that there's also  https://crbug.com/830141  which we're investigating. So far I've only seen it repro noticeably on low power CrOS devices, but the issue is present on and so conceivably affects every platform.

Adding some Hangouts folks.

As per comment #14 we have tested with external/dual monitor and unable to reproduce  form our end on chrome version 66.0.3359.117 using Windows10.Hence adding TE-Hardware-Dependency label as the setup as per C#14 required RX 480 video card with 4 monitors.

@ rdevlin.cronin@chromium.org: Requesting to help in investigation of the attached trace in C#16.

Thanks.!