Remove deprecated string features.

sdk/lib/collection/collections.dart

Index: sdk/lib/collection/collections.dart
diff --git a/sdk/lib/collection/collections.dart b/sdk/lib/collection/collections.dart
index b35a52f168c80ab7bc21b3f495794a091ece0f9f..30e9642289fac87ee9c0190e27d6f5fac00ac6da 100644
--- a/sdk/lib/collection/collections.dart
+++ b/sdk/lib/collection/collections.dart
@@ -131,10 +131,10 @@ class IterableMixinWorkaround {
       }
     }
     if (retained.length == length) return;
+    list.length = retained.length;
     for (int i = 0; i < retained.length; i++) {
       list[i] = retained[i];
     }
-    list.length = retained.length;
   }
 
   /**