1325124 - Youtube becomes blank while on RDM if the user changes between devices

Status: NEW

(DevTools :: Responsive Design Mode, defect, P3)

Description

[Cristian Comorasu, QA [:ccomorasu], Releae Desktop QA - Please contact [e-mail]]

[Affected versions]:
 Fx 52.0a2 (20161219004024)
 Fx 53.0a1 (20161221030226) 

[Affected platforms]:
 Windows 10 x64
 Ubuntu 14.04 LTS
 Mac OS X 10.12

[Steps to reproduce]:
 1. Open Firefox.
 2. Go to "www.youtube.com"
 3. Open RDM (ctrl/cmd+shift+m).
 4. Select any mobile device.
 5. Select any laptop.

[Expected result]:
 The view port displays the site accordingly.

[Actual result]:
 The view port becomes blank.

[Regression range]:
 Last good: 20161013030204
 First bad: 20161014060324
 Pushlog: https://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=f03e2740d604d339ed553dad62a3fc54c317f8fa&tochange=0c899672fff6ae00f5b3affbec48ee4daac35fa1

[Notes]:
 Gif with the issue: http://imgur.com/a/8Ei3i .

Comment 1

[J. Ryan Stinnett [:jryans] (Use needinfo, replies may be slow)]

Thanks for filing, that's definitely a strange one!

Looking at the network logs, it looks like after the mobile device in step 4, we're on the page:

https://m.youtube.com/

and then changing to the laptop device in step 5 causes us to navigate to a URL like:

https://www.youtube.com/feed?action_continuation=1&ctoken=4qmFsgJ3Eg9GRXdoYXRfdG9fd2F0Y2gaZENBWjZSME5wWjBGQlIxWjFRVUZHVmxWM1FVSldWazFCUVZGQ1IxSllaRzlaV0ZKbVpFYzVabVF5UmpCWk1tZEJRVkZCUVVGUlJVTkJRVUZDUlVGQldUVTJjVmh6WTNsak1GRko%253D&feed_name=what_to_watch&itct=CAcQui8iEwiS7ICxzJzRAhVNZ04KHTDsAIg%3D&layout=mobile&tsp=1&utcoffset=-360&app=desktop

which gives a 404 error.

This strange navigation can also be seen if you manually resize the viewport to a large laptop size.  Something about the size change is trigger an action on the page, which leads to this navigation.

In Chrome Canary 57, the same steps don't navigate anywhere.  More investigation needed to find if it's a browser or page error.

This is not a regression, since the device selector is a new feature.