DOMException toString is not correct

LayoutTests/fast/dom/custom/document-register-type-extensions-expected.txt

Index: LayoutTests/fast/dom/custom/document-register-type-extensions-expected.txt
diff --git a/LayoutTests/fast/dom/custom/document-register-type-extensions-expected.txt b/LayoutTests/fast/dom/custom/document-register-type-extensions-expected.txt
index ec52413752965f3278c28e2367d27f15f5d3544b..679457d342ca76bae006220859e8dc68e356fa3b 100644
--- a/LayoutTests/fast/dom/custom/document-register-type-extensions-expected.txt
+++ b/LayoutTests/fast/dom/custom/document-register-type-extensions-expected.txt
@@ -3,7 +3,7 @@ Testing document.register() type extension behaviours through createElement().
 On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".
 
 
-PASS document.register('x-foo', { prototype: Object.create(HTMLDivElement.prototype) }) threw exception Error: InvalidStateError: DOM Exception 11.
+PASS document.register('x-foo', { prototype: Object.create(HTMLDivElement.prototype) }) threw exception InvalidStateError: An attempt was made to use an object that is not, or is no longer, usable..
 PASS fooNewed.outerHTML is '<x-foo></x-foo>'
 PASS fooNewed instanceof fooConstructor && fooNewed instanceof HTMLElement is true
 PASS fooNewed instanceof HTMLUnknownElement is false
@@ -48,13 +48,13 @@ PASS fooCreatedNull.outerHTML is '<x-foo></x-foo>'
 PASS fooCreatedNull instanceof fooConstructor is true
 PASS fooCreatedEmpty.outerHTML is '<x-foo></x-foo>'
 PASS fooCreatedEmpty instanceof fooConstructor is true
-PASS document.createElement('@invalid', 'x-bar') threw exception Error: InvalidCharacterError: DOM Exception 5.
+PASS document.createElement('@invalid', 'x-bar') threw exception InvalidCharacterError: An invalid or illegal character was specified, such as in an XML name..
 PASS fooCreatedNS.outerHTML is '<x-foo></x-foo>'
 PASS fooCreatedNS instanceof fooConstructor is true
 PASS barCreatedNS.outerHTML is '<input is="x-bar">'
 PASS barCreatedNS instanceof barConstructor is true
 PASS isFormControl(barCreatedNS) is true
-PASS document.createElementNS('http://example.com/2013/no-such-namespace', 'xml:lang', 'x-bar') threw exception Error: NamespaceError: DOM Exception 14.
+PASS document.createElementNS('http://example.com/2013/no-such-namespace', 'xml:lang', 'x-bar') threw exception NamespaceError: An attempt was made to create or change an object in a way which is incorrect with regard to namespaces..
 PASS fooParsed instanceof fooConstructor is true
 PASS barParsed instanceof barConstructor is true
 PASS isFormControl(barParsed) is true