Fixes swipe to refresh triggers early when address bar is hidden

[Usiel]

• Do not abort nestedScroll
• Enable swipe to refresh only when no vertical nestedOffset is indicated

Fixes #900

Steps to test this PR:
See #900 linked websites

While this fixes the issue it's not pretty unfortunately. I observed the following behavior with Chrome, but not quite sure how to implement it:

1. Swipe refresh enabled on load
2. User swipes down -> Swipe refresh disabled
3. User swipes up and triggers the overscroll animation (swipe refresh still disabled)
   a) If user swipes up again while the overscroll animation is active -> Swipe refresh stays disabled
   or
   b) Overscroll animation finishes -> Swipe refresh enabled

[JeffAment]

Thank you for fixing this 🙏 I see what you mean about the overscroll animation, but overall everything works much better with these changes.

I've added two other websites where this is easy to reproduce as an edit to my original post on #900; both of these sites also behave much better after these changes, and the issue only seems to happen when the overscroll animation is still active, though I do wonder if checking whether the address bar is fully docked via an offsetChangedListener etc. before enabling swipe to refresh would help this further, as the hidden address bar still seems to be the common denominator. Great work 👍

[cmonfortep]

LGTM, I agree there are still some user events that trigger the pull to refresh when it was not expected (hard to reproduce them) but, like @JeffAment already said, this is definitely an improvement compared to the previous experience, so really good job here for the quickest contribution.

[cmonfortep]

@Usiel going to merge this PR as I don't want to delay the fix for our users.
The idea of @JeffAment about checking if the toolbar is fully shown seems interesting and maybe we want to explore it too. So if anyone has the time for that, feel free to go for it, I'm happy to review it or give support there.

[Usiel]

@cmonfortep Sure makes sense. I'll see if I can tinker with Jeff's idea in the next few days and achieve a cleaner behavior hopefully (both code and UI).