Implement getRange (returning an Iterable).

sdk/lib/collection/list.dart

Index: sdk/lib/collection/list.dart
diff --git a/sdk/lib/collection/list.dart b/sdk/lib/collection/list.dart
index 62bd84c5345e30111104f108799dc79c86936f01..dbf3355d8901cfc77ead2ceb8a5e5eec86a58db4 100644
--- a/sdk/lib/collection/list.dart
+++ b/sdk/lib/collection/list.dart
@@ -364,7 +364,15 @@ abstract class ListMixin<E> implements List<E> {
     return result;
   }
 
-  List<E> getRange(int start, int length) => sublist(start, start + length);
+  Iterable<E> getRange(int start, int end) {
+    if (start < 0 || start > this.length) {
+      throw new RangeError.range(start, 0, this.length);
+    }
+    if (end < start || end > this.length) {
+      throw new RangeError.range(end, start, this.length);
+    }
+    return new SubListIterable(this, start, end);
+  }
 
   void insertRange(int start, int length, [E initialValue]) {
     if (start < 0 || start > this.length) {