User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:79.0) Gecko/20100101 Firefox/79.0

Steps to reproduce:

1. open any extension page
2. go "github.com"
3. click back

• refresh the page (F5)
• or click Forward and Back again
• or go to some other page and return back

Actual results:

Tab is broken. Extension page will not work, refreshing won't help.

Expected results:

Extension should not break.

This is a regression in new 79.0b1, Nightly 80.0a1 is also affected. Release 78 is ok.

This greatly affects all extensions overriding New tab page!

Additionally broken tab will no longer execute content scripts (of all extensions on any page).

Fixed by 79.0b2 release.
Nightly is still affected.

Steps to reproduce:

1. Install Foxy Gestures

2. Open Option page of the extension
   about:addons > Extensions > Click [...] button of Foxy Gestures > Choose Options

3. Open https://archive.mozilla.org/pub/firefox/releases/ in the same tab

4. Perform mouse gesture of History Back(←)
   --- observe, the extension's option page displayed properly --- no Bug.

5. Repeat Step 3 and Step 4
   Open https://archive.mozilla.org/pub/firefox/releases/ in the same tab
   Perform mouse gesture of History Back(←)
   --- observe, the extension's option page is broken --- Bug appears.

Regression window:
https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=61bdbb94ab7abd434c60e2a40fa9f07b11237ebb&tochange=9b3cf2944aa064c840285247fa62cdf26e203935

I'm sure there's an underlying problem causing bugs like this one and bug 1647205. With BC preservation there's a bunch of problems as tabs do process switches but maintain their browsing context and/or frame loader. I'm investigating.

Set release status flags based on info from the regressing bug 1550571

The regressing change has been disabled in beta.

This has been fixed by Bug 1599579