Change the field and constructor parameter types of NoSuchMethodError to Symbol.

pkg/unittest/test/matchers_minified_test.dart

Index: pkg/unittest/test/matchers_minified_test.dart
diff --git a/pkg/unittest/test/matchers_minified_test.dart b/pkg/unittest/test/matchers_minified_test.dart
index 787c9e1b4b985ae361e8f6a1496bd087d29e5848..0edd3e35f7064b19fa46f73ce8eced238bde78da 100644
--- a/pkg/unittest/test/matchers_minified_test.dart
+++ b/pkg/unittest/test/matchers_minified_test.dart
@@ -52,8 +52,9 @@ void main() {
     });
 
     test('throwsNoSuchMethodError', () {
-      shouldPass(() { throw new NoSuchMethodError(null, '', null, null); },
-          throwsNoSuchMethodError);
+      shouldPass(() {
+        throw new NoSuchMethodError(null, const Symbol(''), null, null);
+      }, throwsNoSuchMethodError);
       shouldFail(() { throw new Exception(); },
           throwsNoSuchMethodError,
           matches(