Fenix: [Pull To Refresh][Bug] overscroll-behavior: none must disable pull-to-refresh

[mstange]

Steps to reproduce

1. Load this testcase
2. Attempt a pull-to-refresh gesture.

Expected behavior

No pull to refresh should be triggered, because the page is using overscroll-behavior: none.

Actual behavior

Pull to refresh triggers, incorrectly.

Device information

• Android device: Moto G5
• Fenix version: Nightly 201112

Honoring overscroll-behavior: none is a requirement for web compatibility. This property is used, for example, on pages which implement their own built-in pull to refresh gesture handling.

[Mugurell]

First I thought that GV should just return HANDLE_CONTENT.
But it should do this only if the page is scrolled to the top.
Which I think would complicate things..
@hiikezoe @theres-waldo Do you think GV should handle this? That CSS would complicate things even more on Fenix.

[theres-waldo]

GV has access to information like "are we scrolled to the top", so it could handle this, yes.

I think a good start here would be to:

1. Agree on a place where the expected behaviour of the flags (i.e., under which circumstances each one is returned) is documented precisely. (At the declarations in PanZoomController.java perhaps? Or it could be somewhere else if that's too "internal to GV".)
2. Propose a patch to the descriptions mentioning overscroll-behavior.
3. We will try to change the GV behaviour to match the new descriptions.

[Mugurell]

GV has access to information like "are we scrolled to the top", so it could handle this, yes.

I think a good start here would be to:

1. Agree on a place where the expected behaviour of the flags (i.e., under which circumstances each one is returned) is documented precisely. (At the [declarations in PanZoomController.java](https://searchfox.org/mozilla-central/rev/ff82c973f8ccb0475ec32439e9ec07014b3a681f/mobile/android/geckoview/src/main/java/org/mozilla/geckoview/PanZoomController.java#66) perhaps? Or it could be somewhere else if that's too "internal to GV".)

Using PZC as the source of truth for these flags seems good to me.
In AC we are already mapping those flags to our own which could maybe have better descriptions.
(The mapping is done for ease of use in constructs like engineView.getInputResult)

2. Propose a patch to the descriptions mentioning `overscroll-behavior`.

I don't see why Fenix / AC would be interested in these kind of properties.
Maybe returning the same "HANDLE_CONTENT" would work for these also?

[hiikezoe]

2. Propose a patch to the descriptions mentioning `overscroll-behavior`.

I don't see why Fenix / AC would be interested in these kind of properties.
Maybe returning the same "HANDLE_CONTENT" would work for these also?

Because even if the root element has overscroll-behavior:none, there are cases that Fenix should move the dynamic toolbar in the case, say a content height is over 100vh.

[hiikezoe]

Filed a GeckoView bug https://bugzilla.mozilla.org/show_bug.cgi?id=1678505