Cristian Fogel [:cfogel] Reporter
	Description • 6 years ago

[Affected versions]:
- 64.0a1 (2018-09-19)

[Affected platforms]:
- Win 10x64, Ubuntu 16.04LTS, macOS 10.9

[Steps to reproduce]:
1. Launch Firefox with a fresh profile;
2. Access the about:newtab page;
3. Press F12 on the keyboard;
4. Click on the RDM button;

[Expected result]:
- the newtab / activity steam page is displayed;

[Actual result]:
- page content is empty;

[Regression range]:
- for some reason I was unable to reproduce the issue via mozregression so I downloaded manually builds from https://archive.mozilla.org

- build id for the 1st found - affected version 20180919003800
- https://archive.mozilla.org/pub/firefox/nightly/2018/09/2018-09-04-22-01-34-mozilla-central/

[Additional notes]:
- attached screenshot with the issue;
- happens with fresh profiles;
- workaround is repeating step 2 / pressing the home button;
- other pages don't appear to be affected by this issue

	Jason Duell
	Comment 1 • 6 years ago

Gabriel:  how important is this?  Looks like we have an implicit range request (i.e. 1st version affected)

	Patrick Brosset <:pbro>
	Comment 2 • 6 years ago

I tried to reproduce this without any luck so far (both times on macOS, with a fresh profile, reloading the page several times):
- tested on the latest nightly from today, and the page did appear normally
- tested on the affected version 20180919003800 (downloaded from the URL provided above), and it worked fine there too. Now, that nightly version crashed for me shortly after confirming that the scenario worked. Cristi didn't say that there was a crash, so this is probably unrelated.

If anybody can reproduce, please open the browser console (ctrl+shift+J) and check if there are errors in there.

	Cristian Fogel [:cfogel] Reporter
	Comment 3 • 6 years ago

Attached recording, made with 64.0a1 (2018-09-26) on win10.

	J. Ryan Stinnett [:jryans] (Use needinfo, replies may be slow)
	Comment 4 • 6 years ago

This is the expected behavior with RDM and about:newtab in Firefox 62 or later.  Please see bug 1470497 and bug 1453519.  :cfogel and I discussed this behavior bug 1470497 comment 14.

It's a workaround that we apply because of about:newtab loading in a special process, which conflicts with RDM.  To reproduce the situation, you must have preloading enabled[1] and you typically need to load a second tab in a browser window.  In the Browser Console, check `gBrowser.selectedBrowser.hasAttribute("preloadedState")`.  If it's true, the tab is preloaded, and you should see white content inside RDM, which is the expected workaround behavior[2].

[1]: https://searchfox.org/mozilla-central/rev/ce57be88b8aa2ad03ace1b9684cd6c361be5109f/browser/base/content/tabbrowser.js#1767
[2]: https://searchfox.org/mozilla-central/rev/ce57be88b8aa2ad03ace1b9684cd6c361be5109f/devtools/client/responsive.html/browser/swap.js#108-122

	Cristian Fogel [:cfogel] Reporter
	Comment 5 • 6 years ago

Lost track of this one, thanks!

	karbazol666
	Comment 6 • 6 years ago

Comment on attachment 9012494 [details]
rdm_empty.gif

Спасибо 👍