Support for CSSOM CSSNamespaceRule interface

LayoutTests/css3/supports-cssom.html

Index: LayoutTests/css3/supports-cssom.html
diff --git a/LayoutTests/css3/supports-cssom.html b/LayoutTests/css3/supports-cssom.html
index 508f6c173f419003c2d22ca8b62e7387ed74edad..2dec649db863ecdd69696557c828b4a08803b8f7 100644
--- a/LayoutTests/css3/supports-cssom.html
+++ b/LayoutTests/css3/supports-cssom.html
@@ -96,7 +96,7 @@
 
     debug("\n@charset, @namespace, @import rules are not allowed inside @supports.")
     shouldThrow("rules[0].insertRule('@charset \"UTF-8\"', 2)", '"SyntaxError: Failed to execute \'insertRule\' on \'CSSSupportsRule\': the rule \'@charset \\"UTF-8\\"\' is invalid and cannot be parsed."');
-    shouldThrow("rules[0].insertRule('@namespace \"\"', 2)", '"SyntaxError: Failed to execute \'insertRule\' on \'CSSSupportsRule\': the rule \'@namespace \\"\\"\' is invalid and cannot be parsed."');
+    shouldThrow("rules[0].insertRule('@namespace \"\"', 2)", '"HierarchyRequestError: Failed to execute \'insertRule\' on \'CSSSupportsRule\': \'@namespace\' rules cannot be inserted inside a group rule."');
     shouldThrow("rules[0].insertRule('@import url(\"../fast/cssom/resources/import.css\")', 2)", '"HierarchyRequestError: Failed to execute \'insertRule\' on \'CSSSupportsRule\': \'@import\' rules cannot be inserted inside a group rule."');