Only feedback I've got: when I drop a file from Windows, I see multiple items come through, and they're not all files. I also get a text/uri-list. I'd like to see there be a check here for the `kind` property on each item before trying to call `webkitGetAsEntry`, and above (where you check types[0] only) just go ahead and prevent the default regardless of the types. After all, we also want to suppress the console warning where it tries to open the file into our content window as if it were a Chrome tab.

If this isn't clear, let me know: I can go ahead and merge and then make the changes on my end.