- Prevent getting an unmodifiable list being returned from List.from.

runtime/lib/array_patch.dart

Index: runtime/lib/array_patch.dart
diff --git a/runtime/lib/array_patch.dart b/runtime/lib/array_patch.dart
index 109938bf9d2070ce26c6688a610ce310c8c88365..abe5a193d4aaa9eec261487476bef350ee05b875 100644
--- a/runtime/lib/array_patch.dart
+++ b/runtime/lib/array_patch.dart
@@ -45,6 +45,10 @@ patch class List<E> {
       list.add(e);
     }
     if (growable) return list;
+    if (list.length == 0) {
+      // Avoid getting an immutable list from makeListFixedLength.
+      return new List<E>(0);
+    }
     return makeListFixedLength(list);
   }