The code that calculated whether or not we needed to save the comment models in

the "Edit Review" dialog was saving every comment, because we never fetched the

original extra data (which meant that it was comparing the extra data object

against undefined). This change adds some code to actually assign

this._origExtraData, which fixes the issue.

Ran js-tests
Added some instrumentation and checked that when I had modified (but not

  saved) a comment, it would save it as part of the publish operation, but if I

  hadn't modified it, or if I'd modified and saved it, it would skip that and

  only save the review.