I forgot to mention chosing Chromium as "the preferred web browser" in problem reproduction as it is obvious :)

Thanks for the issue...

As per comment #0, tried to reproduce the issue on reported chromium 70.0.3538.77 using Ubuntu 17.10. Attaching screenshot for reference.
Steps:
1. Installed thunderbird
2. Launched reported chromium and changed to default browser
3. Opened chat and clicked on link in thunderbird
As we have observed that when clicked on link the link gets invoked on either chrome browser or firefox browser but not in chromium.

@Reporter: Could you please check the attached screenshot and let us know if anything missed from our end.

Thanks..!



  

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Hi,

First of all, although Ubuntu based,I use Linux Mint 19 with cinnamon, not Ubuntu. I asume,before you have clicked the link in thunderbird, you have minimized the chromium window to the side panel. After that, what you have seen should be : clicking the link did not yield a chromium window popping up from the side panel with the www.google.com (your sample link) in it, instead, it should have been opened as minimized in the side panel. I recreated the problem with 'Chrome' 70.0.3538.77 + Linux Mint 19 as well. But I could not be able to recreate the problem with Chrome 70.0.3538.77 + 'Mac OS High Sierra'. This behaviour seems to be related somehow with chrome and OS interaction. It is so annoying that I changed my default browser to Firefox again. I can provide screen shots or perhaps a video if you need? Regards,   

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

Thanks for the Feedback...

As per comment #4, this seems to be related to Linux Mint 19 with cinnamon. Hence adding 'TE-NeedsTriageFromHYD' label and requesting Inhouse team to look into the issue and help further.

@Reporter: It would be really helpful if a screenshot or video is provided, so that we can investigate the issue further.

Thanks..!

Video is attached.

Regards,

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Thanks for the screen-cast...

Able to reproduce the issue on reported chromium 70.0.3538.77 using Ubuntu 17.10. Doesn't repro on chrome stable version 70.0.3578.102. 
Step:
----
1. When trying to bisect the issue > Opened system settings > application > browser > changed chromium to default browser.
2. Opened Thunderbird and clicked on link. 
3. The link gets opened in the already installed stable chromium app in the system but not on the chromium build which is being installed for checking the regression. Removed the stable chromium app completely from the system.
4. Unable to bisect this further as the link gets invoked from chrome browser but not opened on older chromium builds for checking the regression.

Hence, Marking it as untriaged and will provide bisect information and other OS behaviour soon.

Thanks..!

As we are able to reproduce the on reported chromium 70.0.3538.77 and from latest stable 70.0.3538.102 to M-72 (72.0.3616.0) we have seen inconsistent behavior. The link gets opened from chrome and chromium for same build(which is being installed for checking the regression). Hence, requesting someone from respective team to look in to it and adding TE-NeedsTriageHelp label to it.

Thanks..!

Staging on thomasanderson@ for Linux.