Support for CSSOM CSSNamespaceRule interface

Source/core/css/CSSStyleSheet.cpp

Index: Source/core/css/CSSStyleSheet.cpp
diff --git a/Source/core/css/CSSStyleSheet.cpp b/Source/core/css/CSSStyleSheet.cpp
index 71871efde40c748ea039a5f756f3f5a7ae2e5bad..b098d946d5c3062d2215f204a753766beede230d 100644
--- a/Source/core/css/CSSStyleSheet.cpp
+++ b/Source/core/css/CSSStyleSheet.cpp
@@ -292,9 +292,7 @@ unsigned CSSStyleSheet::insertRule(const String& ruleString, unsigned index, Exc
     CSSParserContext context(m_contents->parserContext(), UseCounter::getFrom(this));
     RefPtrWillBeRawPtr<StyleRuleBase> rule = CSSParser::parseRule(context, m_contents.get(), ruleString);
 
-    // FIXME: @namespace rules have special handling in the CSSOM spec, but it
-    // mostly doesn't make sense since we don't support CSSNamespaceRule
-    if (!rule || rule->isNamespaceRule()) {
+    if (!rule) {
         exceptionState.throwDOMException(SyntaxError, "Failed to parse the rule '" + ruleString + "'.");
         return 0;
     }