fix crash on iOS 13

[ealataur]

Fix crash on iOS 13 when app go to background and back it from

Bugsquad edit: Fixes #7966.

[akien-mga]

Could you rebase the branch to remove the unnecessary merge commit? (just git pull --rebase upstream master should be sufficient if you have upstream pointing to godotengine/godot). See https://docs.godotengine.org/en/3.1/community/contributing/pr_workflow.html#mastering-the-pr-workflow-the-rebase

[akien-mga]

Still needs a rebase to squash commits, otherwise changes seem OK if others can confirm that it fixes the bug without introducing performance regressions.

[gerald1248]

@akien-mga which benchmark should we use? I have built iphone.zip with and without the change. I'm happy to run a comparison.

I'm not 100% confident performance is the same (I get weird dropped frames sometimes, but perhaps they were an issue before and I didn't notice?) but the thing is that this addresses a bug that's pretty serious. Every Godot app on iOS13 crashes every time it is closed.

[akien-mga]

Pushed a rebased commit that should be fine to merge.

which benchmark should we use? I have built iphone.zip with and without the change. I'm happy to run a comparison.

I'm not sure, but I guess the changes should be fine. The only performance-impacting change now is the reintroduction of the [drawView] call, which was removed in #32194 but this was likely not the right fix for the bug it tried to address (this PR looks like it might be).

[akien-mga]

Thanks!

[akien-mga]

Cherry-picked for 3.1.2.

[akien-mga]

Cherry-picked for 3.0.7.