Bugzilla

A few additional notes:
(1) I see this same bug on desktop as well.  In Chrome, I can click-and-drag to select text in my Twitter/X DMs, but I can't in Firefox.

(2) Regarding `user-select: text` -- Chrome does actually get `user-select: text` on these buttons **via inheritance** from an ancestor-div that has style set on it, via this rule:
```css
.r-1xnzce8{-moz-user-select:text;-webkit-user-select:text;user-select:text;}
```

That inherits down to these buttons -- but in Firefox, that doesn't help because we override it with the UA stylesheet rule that I linked in the platform bug, which explicitly sets `user-select: none` for buttons.

One possible fix here (either on Twitter/X end or on our own end as an intervention) would be something like the following, targeting https://x.com/messages/*
```css
.r-1xnzce8 button:not(.r-lrvibr) {
  user-select:text;
}
```

The relevance of the selector-pieces there:
* .r-1xnzce8 is the class that defines `user-select: text` (which inherits to button descendants automatically in Chrome, which the site seems to sort-of depend on for this text selection use-case to work)
* .r-lrvibr is a class that the site sets on some buttons (e.g. buttons next to message with 3-dot and heart icons, which appear on hover), which explicitly sets `user-select: none`.  I want to be sure our new rule here doesn't supersede that one; so I'm just excluding buttons with that class.

A few additional notes:
(1) I see this same bug on desktop as well.  In Chrome, I can click-and-drag to select text in my Twitter/X DMs, but I can't in Firefox.

(2) Regarding `user-select: text` -- Chrome does actually get `user-select: text` on these buttons **via inheritance** from an ancestor-div that has style set on it, via this rule:
```css
.r-1xnzce8{-moz-user-select:text;-webkit-user-select:text;user-select:text;}
```

That inherits down to these buttons -- but in Firefox, that doesn't help because we override it with the UA stylesheet rule that I linked in the platform bug, which explicitly sets `user-select: none` for buttons.

One possible fix here (either on Twitter/X end or on our own end as an intervention) would be something like the following, targeting https://x.com/messages/*
```css
.r-1xnzce8 button:not(.r-lrvibr) {
  user-select:text;
}
```

The relevance of the selector-pieces there:
* `.r-1xnzce8` is the class that grants `user-select: text` to some ancestor div (which then inherits to button descendants automatically in Chrome, which the site seems to sort-of depend on for this text selection use-case to work)
* `.r-lrvibr` is a class that the site sets on some buttons (e.g. buttons next to message with 3-dot and heart icons, which appear on hover), which explicitly sets `user-select: none`.  I want to be sure our new rule here doesn't supersede that one; so I'm just excluding buttons with that class.