Bugzilla

Hi Stephen, regarding the two topics:

First one, I was not able to reproduce this locally, I tried some reproducers... but without any luck. 

Regarding the patch, the backwards-incompatible behavior comes from `SetSupportsNativeFullScreen`, 
[SetSupportsNativeFullScreen](https://searchfox.org/firefox-main/rev/9c267d0a950b189974105667e9eb14d2f6172564/xpfe/appshell/AppWindow.cpp#1559) is called always, with true if the attribute `macnativefullscreen` is there (does not matter which value), otherwise it is called with false.

[Only 2 .xhtml](https://searchfox.org/firefox-main/search?q=macnativefullscreen&path=&case=false&regexp=false) use this attribute, in your patch things like: `devtools in window mode`, `more site info`, the enterprise login screen(which we can the macnativefullscreen of course), will show the `+` button.   

Do you want that I try with this patch, or should we refine it?

Hi Stephen, regarding the two topics:

First one, I was not able to reproduce this locally, I tried some reproducers... but without any luck. 

Regarding the patch, the backwards-incompatible behavior comes from `SetSupportsNativeFullScreen`, 
[SetSupportsNativeFullScreen](https://searchfox.org/firefox-main/rev/9c267d0a950b189974105667e9eb14d2f6172564/xpfe/appshell/AppWindow.cpp#1559) is called always, with true if the attribute `macnativefullscreen` is there (does not matter which value), otherwise it is called with false.

[Only 2 .xhtml](https://searchfox.org/firefox-main/search?q=macnativefullscreen&path=&case=false&regexp=false) use this attribute, in your patch things like: `devtools in window mode`, `more site info`, the enterprise login screen(which we can the macnativefullscreen of course), will show the `+` button.   

I did 500 runs, we had 6 tests failures (unrelated) and 0 crashes.
https://firefox-ci-tc.services.mozilla.com/tasks/groups/D5xQcsafQtSvD0wFSIEvHQ#marionette

Hi Stephen, regarding the two topics:

First one, I was not able to reproduce this locally, I tried some reproducers... but without any luck. 

Regarding the patch, the backwards-incompatible behavior comes from `SetSupportsNativeFullScreen`, 
[SetSupportsNativeFullScreen](https://searchfox.org/firefox-main/rev/9c267d0a950b189974105667e9eb14d2f6172564/xpfe/appshell/AppWindow.cpp#1559) is called always, with true if the attribute `macnativefullscreen` is there (does not matter which value), otherwise it is called with false.

[Only 2 .xhtml](https://searchfox.org/firefox-main/search?q=macnativefullscreen&path=&case=false&regexp=false) use this attribute, in your patch things like: `devtools in window mode`, `more site info`, the enterprise login screen(which we can set the macnativefullscreen of course), will show the `+` button.   

I did 500 runs, we had 6 tests failures (unrelated) and 0 crashes.
https://firefox-ci-tc.services.mozilla.com/tasks/groups/D5xQcsafQtSvD0wFSIEvHQ#marionette