Change List.sort to not have a default parameter value.

sdk/lib/core/sequences.dart

Index: sdk/lib/core/sequences.dart
diff --git a/sdk/lib/core/sequences.dart b/sdk/lib/core/sequences.dart
index d671cb5106b3417888b674e7a7d83e345b7602e8..5ad8a3762a0fbc1d10c075daa0baf5e9ad08b27b 100644
--- a/sdk/lib/core/sequences.dart
+++ b/sdk/lib/core/sequences.dart
@@ -153,7 +153,7 @@ class SequenceList<E> extends SequenceCollection<E> implements List<E> {
         "Cannot add to an unmodifiable list");
   }
 
-  void sort([Comparator<E> compare]) {
+  void sort([int compare(E a, E b)]) {
     throw new UnsupportedError(
         "Cannot modify an unmodifiable list");
   }