1f50bf550a
Previously, for optional lists, the absence of a list was treated by the toJson and fromJson methods as equivalent to the presence of an empty list. This disagreed with the API documentation in several places and created the risk of null reference exceptions in clients. This change makes optional lists behave just like optional fields of any other type. BUG=dartbug.com/21230 R=brianwilkerson@google.com Review URL: https://codereview.chromium.org//625413002 git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@40939 260f80e4-7a28-3924-810f-c04153c831b5