teo8976@ Thanks for the issue.

Unable to reproduce the issue on windows 7, Linux Ubuntu 14.04 and Mac 10.11.4 using chrome version 49.0.2623.112 and latest stable 50.0.2661.75 and canary 52.0.2711.0 with the below steps

1. Opened Dev tools
2.Clicked on mobile icon in devtools and slected any mobile device
3.Right click on tab and duplicate
4.Normal new tab opened

Please find the attached screen cast and confirm anything missed here.
Request you please try the issue on latest stable and update the thread with OS details to trigae the issue further.

Thanks,

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Can you try on Ubuntu 15.10?

OMG just had a look at your screencast. Your page doesn't even exceed the screen height, so you obviously have no scrollbars at all. How did you expect that to be a test for a scrollbar-related issue??

Thank you for providing more feedback. Adding requester "kavvaru@chromium.org" for another review and adding "Needs-Review" label for tracking.

For more details visit https://sites.google.com/a/chromium.org/dev/issue-tracking/autotriage - Your friendly Sheriffbot

Thnaks for the update.
Unable to reproduce the issue on windows 7, Linux Ubuntu 14.04 and Mac 10.11.4
using chrome version 50.0.2661.87.Not observed any issue with small browser window.
Please find the attached screen cast.

Request you please provide us any screen shot or video would help us for better understanding the issue.

Thanks,

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604393.ogv 1.4 MB Download

Actually the thin and vanishing scrollbar can be observed in your very screencast at 0:17.

Thanks for the quick update.
Able to reproduce the issue on windows 7, Linux Ubuntu 14.04 using chrome version 50.0.2661.87 and canary 52.0.2715.0.
Able to see the thin scrollbar in new tab.
this is non regression issue from M30 builds.Hence marking it as Untriaged to get more inputs from dev team.

Thanks,

I don't mean to be rude, but if you had actually read the report and tested the issue with a minimum of attention, this could have been confirmed since day 1 without asking the original reporter (in this case, me) *twice* for additional information, whci wasn't "additional" at all.

What worries me is that I have seen the exact same happen with another bug report of mine (namely 604074). In both cases I struggle to see what may have not been sufficiently clear in the original reports.

I am also observing a related, sort of the-other-way-around issue, though I haven't found a way of systematically reproduce it, and it doesn't  seem to involve duplicating tabs.

At random times, after turning mobile emulation off and on, or after reloading the page with mobile emulation on, EITHER or both of the following happen:
- in the emulated mobile screen, I observe desktop-like thick scrollbars (overlapping with the expected thin autohide touchscreen-like scrollbars);
- the cursor pointer is a regular arrow pointer rather than a circle

Some random combination of refreshing and switching mobile emulation off and on again and again, usually ends up "fixing" the issue.

Reproduced on Linux stable 50.0.2661.75. Good catch. It looks like we're not resetting some of the mobile emulation settings when we duplicate a tab. +dgozman@ for DevTools attention.

This is a flaw of current design - we enable overlay scrollbar for a renderer process, and duplicated tab is in the same process. This will not be fixed soon, as it requires substantial redesign.

Are you sure?

This is NOT specific to duplicating tabs.

Every time you switch mobile emulation on or off in the Developer Tools (or you open/close the Developer tools when they have mobile emulation on), all the scrollbars that are already visible will fail to be updated to the new mode. 

However, scrollbars that appear afterwards will be rendered as expected. You can end up with a mix of regular scrollbars and overlay scrollbars.

Indeed, when there are scrollbars that have been rendered in the wrong mode (e.g. they showed up when you were in mobile mode so they are overlay scrollbars, then you switch to regular screen mode and the scrollbars remain overlay), if you enlarge the window so that the scrollbars disappear, and then shrink the window again, the scrollbars will reappear in the expected mode.

To me it looks more like you forget to update existing scrollbars, than anything related with processes.

What you describe in #c14 is a separate issue, which we are aware of. It has the same cause of "overlay scrollbars" flag being static global. The workaround is to reload the page after engaging with mobile emulation.

Why the f*** was this archived?

> This is a flaw of current design [...] it requires substantial redesign

Then do the redesign. This bug is tremendously annoying. And it persists after reloading the page.

It has slightly changed: the scrollbar observed at step 3 in the duplicated tab, now is no longer thin and doesn't auto-hide. It has the thickness of a regular desktop scrollbar, but the alpha of a touchscreen scrollbar, it has no background or up/down buttons, and sometimes (randomly) it becomes transparent to clicks so you can't use it. There's no workaround except closing the tab, copying the url and opening a new tab.