Classes: Add test for method prototype

Methods should not have a prototype property

BUG=v8:3330
LOG=y
R=dslomov@chromium.org

Review URL: https://codereview.chromium.org/678103004

Cr-Commit-Position: refs/heads/master@{#24939}
git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24939 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

test/mjsunit/harmony/classes.js

@@ -172,6 +172,7 @@ function assertMethodDescriptor(object, name) {
   assertTrue(descr.enumerable);
   assertTrue(descr.writable);
   assertEquals('function', typeof descr.value);
+  assertFalse('prototype' in descr.value);
 }
 
 function assertGetterDescriptor(object, name) {