Use UnmodifiableListView to expose read-only lists.
Use UnmodifiableListView to expose read-only lists.

Review URL: https://codereview.chromium.org//14394003

git-svn-id: 23a8f5f0d54e45b03616c23fdace24df99c52d8d@21855 260f80e4-7a28-3924-810f-c04153c831b5

dart-lang/stack_trace