Refactor linkage from ChangeScreen2 and its Reviewers widget

Move the loop that splits the reviewer and CC list into the Reviewers
widget, eliminating a duplicated block of code.

Link the widget with its sibling reviewersText in the init() method
rather than set(), matching the pattern used in Labels widget.

Change-Id: Iebc74f60781140d7a3b8643aed9f2dbb74e4e889
3 files changed