b3cb27a829
CreateTypeMirror is already factored out of MethodMirror_return_type since it is needed by others mirrors (future CLs). Also introduces CreateMirror() which will be used in future CLs. BUG= R=asiva@google.com Review URL: https://codereview.chromium.org//19780002 git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@25252 260f80e4-7a28-3924-810f-c04153c831b5