Make String.fromCharCodes take start/end.

sdk/lib/internal/iterable.dart

Index: sdk/lib/internal/iterable.dart
diff --git a/sdk/lib/internal/iterable.dart b/sdk/lib/internal/iterable.dart
index 006b31acb6fef4ee6860799d8135c2c10c6b1cfe..78cebced560803c219dfc51a76f37b55fde7eab8 100644
--- a/sdk/lib/internal/iterable.dart
+++ b/sdk/lib/internal/iterable.dart
@@ -226,7 +226,7 @@ abstract class ListIterable<E> extends IterableBase<E>
 }
 
 class SubListIterable<E> extends ListIterable<E> {
-  final Iterable<E> _iterable;
+  final Iterable<E> _iterable;  // Has efficient length and elementAt.
   final int _start;
   /** If null, represents the length of the iterable. */
   final int _endOrLength;
@@ -293,6 +293,21 @@ class SubListIterable<E> extends ListIterable<E> {
       return new SubListIterable<E>(_iterable, _start, newEnd);
     }
   }
+
+  List<E> toList({bool growable: false}) {
+    int start = _start;
+    int end = _iterable.length;
+    if (_endOrLength != null && _endOrLength < end) end = _endOrLength;
+    int length = end - start;
+    if (length < 0) length = 0;
+    List result = growable ? (new List<E>()..length = length)
+                           : new List<E>(length);
+    for (int i = 0; i < length; i++) {
+      result[i] = _iterable.elementAt(start + i);
+      if (_iterable.length < end) throw new ConcurrentModificationError(this);
+    }
+    return result;
+  }
 }
 
 /**