Fix stack trace accessor behavior.

test/mjsunit/stack-traces.js

Index: test/mjsunit/stack-traces.js
diff --git a/test/mjsunit/stack-traces.js b/test/mjsunit/stack-traces.js
index 46a16eb87a2db857a00f8d7de060af09ffc2fa00..f80a627b24a87eae9fe00e5bd0a24c5b7f5af903 100644
--- a/test/mjsunit/stack-traces.js
+++ b/test/mjsunit/stack-traces.js
@@ -331,3 +331,23 @@ Error.prepareStackTrace = function() { Error.prepareStackTrace = "custom"; };
 new Error().stack;
 
 assertEquals("custom", Error.prepareStackTrace);
+
+// Check that the formatted stack trace can be set to undefined.
+error = new Error();
+error.stack = undefined;
+assertEquals(undefined, error.stack);
+
+// Check that the stack trace accessors are not forcibly set.
+var my_error = {};
+Object.freeze(my_error);
+assertThrows(function() { Error.captureStackTrace(my_error); });
+
+my_error = {};
+Object.preventExtensions(my_error);
+assertThrows(function() { Error.captureStackTrace(my_error); });
+
+var fake_error = {};
+my_error = new Error();
+var stolen_getter = Object.getOwnPropertyDescriptor(my_error, 'stack').get;
+Object.defineProperty(fake_error, 'stack', { get: stolen_getter });
+assertEquals(undefined, fake_error.stack);