Unable to reproduce the issue on Win-7 and Win-10 using chrome reported version #63.0.3239.108 and latest canary #65.0.3310.0.

Attached a screen cast for reference.

Following are the steps followed to reproduce the issue.
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1. Installed the Google Keep Chrome Extension in Chrome.
2. Clicked on the extension icon in the toolbar.
3. Once the popup loaded, tried to close it by clicking away from it.
4. Observed that extension popup closed simply by clicking away from it as expected.

reporter@ - Could you please check the issue on latest canary #65.0.3310.0 by creating a new profile without any apps and extensions and please let us know if the issue still persists or not.

Thanks...!!

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My issue only occurs when the extensions prompts that I need to sign in (I have actually never signed into it for all of this time, so I don't know if I'd also have the issue when signed in), and it does go away when double-clicking elsewhere, but not single-clicking elsewhere.

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Thank you for providing more feedback. Adding requester "krajshree@chromium.org" to the cc list and removing "Needs-Feedback" label.

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

Unable to reproduce the issue on reported chrome version 63.0.3239.108 and on the latest canary 65.0.3324.0 using Windows 10. Checked as per the comment#3c by reporter with out sing-in into the account. Followed the below mentioned steps.
1. Launched chrome and added the extension using the URL provided in comment#0
2. Clicked on the extension icon in the toolbar
3. Once the popup loaded, tried to close it by clicking away from it
We observed that the pop-up closed with a single click rather than taking two clicks. Attaching the screen cast for reference.

@Reporter: Could you please check the screen cast and let us know if there is any way to be followed in order to reproduce the issue. Any further inputs from your end may help us.

Thanks! 

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In order to reproduce, you have to try to click underneath the popup. If you click left of the popup, it closes. It is also obsessed with opening and then immediately closing when clicking on its icon.

Thank you for providing more feedback. Adding requester "vamshi.kommuri@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

Could someone triage this?

Unable to reproduce the issue on latest chrome stable# 66.0.3359.170 with steps mentioned in comment#0

@Reporter: Could you please try to test this issue on latest chrome stable and let us know if the issue still persists, if possible could you please provide screencast of the issue which help in better understanding. You can download latest chrome stable from URL: https://www.chromium.org/getting-involved/dev-channel.

Thanks!

Did you refer to comment 6?

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

Able to reproduce the issue on reported chrome version 63.0.3239.108 & latest stable 66.0.3359.181  and on latest chrome 68.0.3433.0 using ubuntu 14.04,Windows 10 and Mac 10.13.1. 
 
Same behavior is seen on M60(60.0.3112.113) hence considering it as non-regression and marking it as Untriaged.

Note: This issue reproducible when we click on Google Keep extension second time and observe the issue as per comment #6.

Thanks! 

As far as I can tell, keep extension isn't using extension's default popup mechanism (notice that it renders differently from other extensions with popup), so file an issue on keep issue tracker?