The problem is that the text of popup is not clear:

The text say: "You can install Firefogg (a Firefox extension) to automatically convert your file." -> no i can't i have chrome :(

It should say: "if you are on mozilla firefox browser, you can install Firefogg extension ..."
"If you have another browser, ..."

the way it is said is important. Imagine :

• people don't know firefox,
• people don't know that firefox is the same as mozilla,
• people think "hey perhaps i could install a module firefox on chrome", "perhaps i can use a firefox extension with any browser",
• "i don't know what is firefox extension, but if it proposed to me, it is because i can (it is written "you can")".

i understand it is the same popup for any browser, but if so it need to be clear. (or a popup different per browser).

screenast to see popup (on chrome): https://commons.wikimedia.org/wiki/File:Commonfirefogg.webm