addElementDelete = function () {
            if (!newNodeMap[oldChild.tagID]) {
                // We can finalize existing edits relative to this node *before* it's
                // deleted.
                finalizeNewEdits(oldChild.tagID, true);

                newEdit = {
                    type: "elementDelete",
                    tagID: oldChild.tagID
                };
                newEdits.push(newEdit);

                // deleted element means we need to move on to compare the next
                // of the old tree with the one from the current tree that we
                // just compared
                oldIndex++;
                return true;
            }
            return false;
        }
If the old element that we're looking at does not appear in the new
DOM, that means it was deleted and we'll create an elementDelete edit.

If the element is in the new DOM, then this will return false and
the main loop with either spot this node later on or the element
has been moved.

@return {boolean} true if elementDelete was generated