Test for immutable Lists in ListSet API methods.

runtime/bin/file.cc

Index: runtime/bin/file.cc
diff --git a/runtime/bin/file.cc b/runtime/bin/file.cc
index 58817ea629538ad9744e439ed1897d01e9dfdac5..07201c6e9fdecf669c9657f7134234da7e41132e 100644
--- a/runtime/bin/file.cc
+++ b/runtime/bin/file.cc
@@ -159,8 +159,9 @@ void FUNCTION_NAME(File_ReadList)(Dart_NativeArguments args) {
     if (total_bytes_read >= 0) {
       result =
           Dart_ListSetAsBytes(buffer_obj, offset, buffer, total_bytes_read);
-      ASSERT(!Dart_IsError(result));
-      return_value = total_bytes_read;
+      if (!Dart_IsError(result)) {
+        return_value = total_bytes_read;

[turnidge, 2011/11/16 18:50:18]

There's probably some good diagnostic information for the user in
Dart_GetError(result).  Perhaps not useful in this case though.  Up to you.

+      }
     }
     delete[] buffer;
   }