Bug 1093219 - m3u parsing

This method is broken in multiple ways:
1) you're looking for an absolute path, but you store the songs as relative paths
2) I think your filter call is only returning elements where the paths match rather than elements that do not match. 
3) By using filter() you're creating a whole new array rather that just modifying an existing array in place, which will have worse performance.

If you switch to just using an array of filenames, then you can use the new Array.indexOf() method to find the song to remove and Array.splice() to remove it.

Note that you should also think about (and document) what this method should do when a playlist contains the same song more than once.

Also, will the music app need a method to remove a song by its position within the playlist instead of by its filename. I suspect you'll need that.