Comment 0 for bug 677551

It seems like there is an n^2 algorithm somewhere causing adding and removing newlines to <textarea>s with lots of lines (or maybe just lots of text) to very slow.

Steps to reproduce:
1. Go to https://bugzilla.mozilla.org/attachment.cgi?id=476443&action=edit
2. Click "Edit Attachment As Comment"
3. Click in the textarea
4. Press enter

Step 4 is very noticeably slow.

Similarly

5. Select a few lines of text
6. Press delete

is similarly slow.

Normal editing is fast, however any time newlines are added or removed there is a significant pause.

This is a recent regression so I'm guessing it's a regression from bug 240933. I've only tested on mac so not sure if it happens on other platforms or not.