Fix JS error trying to access this.saveDialog from switch to source mode code path

The switch to source mode code path was causing onSerializeComplete to
be called, which accesses this.saveDialog because it assumes it's being
called from onSaveDialogReview.

In fact, onSaveDialogReview was calling it twice, once as the callback
it passes to serialize() and once in response to the serializeComplete
event. Cleaned this up by renaming the function and removing the
event binding, so it's now only called once and only for reviewing
changes to new pages, not in the switch to source mode code path.

Bug: 62544
Change-Id: I86eea57806a20408c8dc89a234c39cae1d969bca
Merge "Fix JS error trying to access this.saveDialog from switch to source mode code path"