Demo page at http://incaseofstairs.com/jsdiff/ renders newlines wrong on Firefox

[ExplodingCabbage]

Steps to repro:

• Open the page in Firefox
• Populate the first input box with a single line of text (if that's not how it is already)
• Press the Enter key to insert a newline
• Observe that the single line break that got entered had height equal to the entire height of the input box, and that the initial line of text has been scrolled off-screen.

Not sure of the cause yet. Googling stuff about contenteditable and Firefox I see some Stack Overflow posts about newlines being handled differently between Firefox and Chrome but I dunno if it's up to date nor if it's pertinent to the specific behaviour described above; I will have to dig into it.