I've experienced this crashing several times as well recently. Most recently, this morning it crashed ~~2~~ 3 times (after the first 2 times, I was unable to reproduce it for a while, but I kept trying and eventually did a 3rd time) in a row while attempting the exact same thing: when I started typing "in" in the tag search/dropdown/autocomplete (it don't remember if it was when I stopped at "in" or when I typed a 3rd letter that never showed up), it showed a large list of matches, like this:

but then immediately froze (not only this website but all 29 other open Chrome windows also froze). The text cursor continued blinking but everything became non-responsive.

Exactly the same as @chrisaldrich:
- This only occurs when adding a tag to an annotation.
- This is with the Chrome extension (haven't tried to reproduce with the bookmarklet)
- I don't recall any other website that has managed to completely freeze up Chrome like this
- I never experienced this with earlier versions of this client, prior to the various changes the tag UI underwent in the last 3 or so months.

It's getting to the point where I'm hesitant to start typing in the tag entry field for fear of it crashing. Sometimes, to be "safer", I type out my tag search string in another field (like the Description field) and then paste it into the tag field to avoid triggering a search with too many tag matches from only searching on the first couple characters.

I suspect this issue is a result of the confluence of the following factors:
- I have added a lot of tags via Hypothesis (that's mostly what I use it for) so when it searches for matching tags for a short substring like "in", it probably gets back a lot of tags.
- The H client seems to starts searching immediately. I would prefer that it had a longer debounce delay and/or didn't start searching until I had typed 3 or more characters. That would probably also help it feel less laggy when you first start typing a tag sometimes.
- I have no idea, but maybe there is some bug in the client whereby each keystroke causes exponentially more queries to be sent off or something? (I don't know how to see network requests from extensions in Network tab.) Maybe a new callback gets added each time without clearing the previous callbacks, or calls itself recursively, or ...?
- I suspect the crash occurs for a cache miss and when I've been unable to reproduce it, I suspect it's because the list of tags for my search string have already been cached in the client?

I'm running:
- Hypothesis version: 1.272.0
- Chrome Version 79.0.3945.79 (Official Build) Built on Ubuntu , running on Ubuntu 18.04 (64-bit)