Scrolling issue on mobile highlighting using via with Chrome and Brave browsers

### Steps to reproduce

1. On mobile version of Chrome using the via.hypothes.is prefix to activate Hypothesis on any website.
2. I try to highlight a specific piece of text beyond a single word.

### Expected behaviour
I would expect to be able to slowly and accurately highlight a specific piece of text.

### Actual behaviour
Once I’ve got a small piece of text highlighted and try to expand it with the “handlebars” to go either up or down the page, generally beyond text on the same line, the cursor jumps immediately down to the very bottom of the page and it becomes essentially possible to select a particular block of text.

### Browser/system information
Chrome browser v 86.0.4240.75 on Android 9

### Additional details
I’ve experienced this before on earlier versions of Chrome/Android. I’m not aware of it having ever worked properly before. I don’t experience the same issue on the mobile version of Firefox on the same phone.

[@williamgunn](https://github.com/williamgunn) has reported a similar bug when using the Brave browser as well at:
[https://boffosocko.com/2020/05/24/a-hack-for-using-hypothes-is-to-annotate-on-mobile/#comment-300981](https://boffosocko.com/2020/05/24/a-hack-for-using-hypothes-is-to-annotate-on-mobile/#comment-300981)

(Originally published at: https://boffosocko.com/?p=55778428)