Unable to reproduce the issue on reported chrome version 63.0.3239.84 using Mac 10.13.1, we have tried to reproduce the issue with gmail page with the steps mentioned below, we haven't faced any scrolling focus:

Steps followed to reproduce the issue:
1) Logged in to gmail with two valid credentials
2) Clicked on profile icon to switch identities
3) Clicked on second ID
4) Didn't observed any scrolling focus on second ID

@Reporter:
Can you please  provide the URL for which you are fracing this issue, that will help in further triaging the issue
Please try to reproduce the issue by creating a new person which donot have apps and extensions on your Mac 10.13.2 and let us know if the issue still persists.

Thanks!

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It happens on focus of the anchor tag, not hover (notice the button animation in my screenshot, the grey oval). Verified it happens on chrome and on Firefox. It happens on both of my identities included in the screenshot. I don't see how my apps or extensions would play a role. 

Note: Right click to inspect, then right click the anchor <a> tag and click on focus. 

On focus of the anchor tag a pseudo-element is displayed with absolute positioning with the top, left, bottom, and right properties set to a value of -4px causing the overflow. Changing those values to 0 solves the problem as well as setting the overflow property's value to hidden on the anchor tag itself. 

Hope this helps.

+shend@ - can you help triage? I'm guessing this is a CSS issue but could be wrong.
Thanks!

Thank you for providing more feedback. Adding requester "sc00335628@techmahindra.com" to the cc list and removing "Needs-Feedback" label.

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

Can reproduce on 63.0.3239.84 (Official Build) (64-bit). Focusing on the alternate identity (e.g. by right clicking or by forcing :focus with devtools) causes scrollbars to appear and the box becomes scrollable.

On the surface this doesn't seem like a bug with the browser but a bug with inbox.

Assigning to Tab to confirm this. Specifically, as wdugan mentioned, :focus causes a ::before pseudo-element to be created with -4px overflows. Do you know if the element becoming scrollable is working as intended? Thanks!

Marking as Hotlist-Interop tentatively.

Yes, if the bottom and right properties are set to -4px, it'll extend into the scrollable area, and trigger a scrollbar (if 'overflow' is set to a scrollable value) per spec. So this is working as intended.  Inbox needs to fix itself.