Remove AsyncError with Expando.

tests/standalone/io/string_transformer_test.dart

Index: tests/standalone/io/string_transformer_test.dart
diff --git a/tests/standalone/io/string_transformer_test.dart b/tests/standalone/io/string_transformer_test.dart
index a15633dd00cb88609d8a3024c68a1f5e12b31ac2..a7dd5443ef6e29cb3c1417bb44b80dc5f2bc6e84 100644
--- a/tests/standalone/io/string_transformer_test.dart
+++ b/tests/standalone/io/string_transformer_test.dart
@@ -197,9 +197,9 @@ testErrorHandler() {
       onDone: () {
         Expect.equals(1, errors);
       },
-      onError: (e) {
+      onError: (error) {
         errors++;
-        Expect.isTrue(e.error is TestException);
+        Expect.isTrue(error is TestException);
       });
   controller.addError(new TestException());
   controller.close();
@@ -222,7 +222,7 @@ testLatin1EncoderError() {
       Expect.fail("data not expected");
     },
     onError: (error) {
-      Expect.isTrue(error.error is FormatException);
+      Expect.isTrue(error is FormatException);
     });
 
 }