Recommit changing List.skip/take/revert returns Iterable and remove mappedBy.

samples/swarm/swarm_ui_lib/observable/observable.dart

Index: samples/swarm/swarm_ui_lib/observable/observable.dart
diff --git a/samples/swarm/swarm_ui_lib/observable/observable.dart b/samples/swarm/swarm_ui_lib/observable/observable.dart
index 06931db0fda5df7351313c646ce107449fb25aab..9ef6533b468e7fdb7104584fa8af51a3cb21b437 100644
--- a/samples/swarm/swarm_ui_lib/observable/observable.dart
+++ b/samples/swarm/swarm_ui_lib/observable/observable.dart
@@ -162,7 +162,7 @@ class ObservableList<T>
     recordGlobalChange();
   }
 
-  List<T> get reversed => _internal.reversed;
+  Iterable<T> get reversed => _internal.reversed;
 
   void sort([int compare(var a, var b)]) {
     if (compare == null) compare = Comparable.compare;
@@ -284,7 +284,6 @@ class ObservableList<T>
   // Collection<T>:
   Iterable<T> where(bool f(T element)) => _internal.where(f);
   Iterable map(f(T element)) => _internal.map(f);
-  List mappedBy(f(T element)) => _internal.mappedBy(f);
   Iterable expand(Iterable f(T element)) => _internal.expand(f);
   List<T> skip(int count) => _internal.skip(count);
   List<T> take(int count) => _internal.take(count);