Disallow assignment to a top level method in dartc

tests/language/src/AssignInstanceMethodNegativeTest.dart

Index: tests/language/src/AssignInstanceMethodNegativeTest.dart
diff --git a/tests/language/src/AssignInstanceMethodNegativeTest.dart b/tests/language/src/AssignInstanceMethodNegativeTest.dart
index f426fca77136cf96506dcf532b0d062052fee627..46505ae6925adc05c032cc31992121f68824cfd9 100644
--- a/tests/language/src/AssignInstanceMethodNegativeTest.dart
+++ b/tests/language/src/AssignInstanceMethodNegativeTest.dart
@@ -7,15 +7,8 @@ class A {
   imethod() { return 0; }
 }
 
-class AssignInstanceMethodNegativeTest {
-
-  static testMain() {
-    var a = new A();
-    // Illegal, can't change a member method
-    a.imethod = () { return 1; };
-  }
-}
-
 main() {
-  AssignInstanceMethodNegativeTest.testMain();
+  var a = new A();
+  // Illegal, can't change a member method
+  a.imethod = () { return 1; };
 }