Using the per-revision bisect providing the bisect results,
Good build:54.0.2820.0(Revision: 409955).
Bad build: 54.0.2822.0 (Revision:410267).

You are probably looking for a change made after 410227 (known good), but no later than 410228 (first known bad).

CHANGELOG URL:

The script might not always return single CL as suspect as some perf builds might get missing due to failure.

https://chromium.googlesource.com/chromium/src/+log/ae875419ff203324cd94c335695a7f9c0081e197..5b6b548e6ebc2374818b61e14cd315add717f71a

From the CL above, suspecting https://chromium.googlesource.com/chromium/src/+/911a4d605e2c485c0cc9547b084a9a3bd3c2e495

@tommycli - 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.

Review-Url: https://codereview.chromium.org/2210933004

Thanks!

Please get this fixed before M55 hits beta.

M55 Beta launch is coming VERY soon. Please try to have fix merged to M55 branch 2883 before 5:00 PM PT Monday, 10/17/16. Thank you.

Not caused by above CL.

It's a Performance / UI Jank issue.

Root cause is: We are now linking the left-navigation Advanced toggle state to the main page Advanced toggle state.

When we expand the Advanced menu on the left nav, it also triggers the main page's Advanced contents to render. That causes the left nav animation to stutter.

It's techincally correct... it's just slow.

How did you determine this was just stutter? Even at 10% speed the animation is very smooth (but wrong, as in the video).

The effect differs depending on which section is selected. Try the same with "Accessibility" and see how the sub-menu starts at "Accessibility". Looking at the Elements panel (tabindex changes), I wonder if this is a focus issue, maybe causing the sub-menu to "scroll" to the wrong place.

I stand corrected. Running it at 10% does show the animation being actually incorrect rather than an instance of UI Jank.

Thanks for the protip (Dev tools => 3 dot menu => More tools => Animations)

It appears that our menu is working as Polymer intended. The paper-submenu demo shows the same behavior - The expansion is indeed different depending on which sub-item is selected, and sometimes it looks funny.

https://elements.polymer-project.org/elements/paper-menu?view=demo:demo/index.html&active=paper-submenu

Marking tentatively as WONTFIX. Re-open and we'll have to file an upstream issue if we want paper-submenu to behave differently.

re-opening, since michaelpg points out it didn't used to look like this.

Moving Milestone to M56 as M55 is already in stable and issue is specific to Proj-MaterialDesign-WebUI.

Able to reproduce the issue on windows 7 using chrome version 57.0.2978.0.

Could any one from dev team please look into this issue.

Thanks,

This looks right to me, closing.