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

runtime/lib/byte_array.dart

Index: runtime/lib/byte_array.dart
diff --git a/runtime/lib/byte_array.dart b/runtime/lib/byte_array.dart
index d4181b83a780cdb7c0dd79b5487814b586dfa89a..f4d0d3f313580ddfd1f6a747f6c376dbd48d5986 100644
--- a/runtime/lib/byte_array.dart
+++ b/runtime/lib/byte_array.dart
@@ -223,7 +223,8 @@ abstract class _ByteArrayBase {
         "Cannot add to a non-extendable array");
   }
 
-  void sort([Comparator compare = Comparable.compare]) {
+  void sort([int compare(var a, var b)]) {
+    if (compare == null) compare = Comparable.compare;
     coreSort(this, compare);
   }
 
@@ -1767,7 +1768,8 @@ class _ByteArrayViewBase {
         "Cannot add to a non-extendable array");
   }
 
-  void sort([Comparator compare = Comparable.compare]) {
+  void sort([int compare(var a, var b)]) {
+    if (compare == null) compare = Comparable.compare;
     coreSort(this, compare);
   }