Fixes the issue 3300: When a user has a draft review, and opens up the "Edit Review" box to finalize their comments and publish, the "Discard Review" command doesn't confirm at all. This makes it easy to lose work, especially when using the keyboard to move over to the command buttons. (https://code.google.com/p/reviewboard/issues/detail?id=3300)
I added the onDiscardClicked function to the file, its about the same as in draftReviewBannerView.js. Should I somehow refactor the code, that it's usable for both occasions? 

Testing is done on my development server and the fix works well. I didn't notice any abnormal behavior.