Post-Mutation Event checks must re-check document constraints.

LayoutTests/fast/dom/DOMException/prototype-object-expected.txt

Index: LayoutTests/fast/dom/DOMException/prototype-object-expected.txt
diff --git a/LayoutTests/fast/dom/DOMException/prototype-object-expected.txt b/LayoutTests/fast/dom/DOMException/prototype-object-expected.txt
index be6610b354dd8272b695d495b003523ec3f6c401..74cfda362a5ed448bae6f456b2aaa56a8194ce1f 100644
--- a/LayoutTests/fast/dom/DOMException/prototype-object-expected.txt
+++ b/LayoutTests/fast/dom/DOMException/prototype-object-expected.txt
@@ -3,7 +3,7 @@ This tests the prototype chain of DOMException objects.
 On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".
 
 
-PASS e.toString() is "HierarchyRequestError: Failed to execute 'appendChild' on 'Node': The new child element contains the parent."
+PASS e.toString() is "HierarchyRequestError: Failed to execute 'appendChild' on 'Node': Nodes of type '#document' may not be inserted inside nodes of type '#document'."
 PASS Object.prototype.toString.call(e) is "[object DOMException]"
 FAIL Object.prototype.toString.call(e.__proto__) should be [object DOMExceptionPrototype]. Was [object Object].
 PASS Object.prototype.toString.call(e.__proto__.__proto__) is "[object Error]"
@@ -15,7 +15,7 @@ PASS e.HIERARCHY_REQUEST_ERR is e.constructor.HIERARCHY_REQUEST_ERR
 PASS e.HIERARCHY_REQUEST_ERR is 3
 PASS e.code is 3
 PASS e.name is "HierarchyRequestError"
-PASS e.message is "Failed to execute 'appendChild' on 'Node': The new child element contains the parent."
+PASS e.message is "Failed to execute 'appendChild' on 'Node': Nodes of type '#document' may not be inserted inside nodes of type '#document'."
 PASS successfullyParsed is true
 
 TEST COMPLETE