CSS Parser: Support CDO and CDC tokens (<!--, -->)

Source/core/css/parser/CSSParserImpl.cpp

Index: Source/core/css/parser/CSSParserImpl.cpp
diff --git a/Source/core/css/parser/CSSParserImpl.cpp b/Source/core/css/parser/CSSParserImpl.cpp
index 3987786d64c1312acca2d4cc223e4d2ee47a4774..e25b2329de6aa69a2759c9ca6c7fb2a350e28472 100644
--- a/Source/core/css/parser/CSSParserImpl.cpp
+++ b/Source/core/css/parser/CSSParserImpl.cpp
@@ -159,8 +159,14 @@ WillBeHeapVector<RefPtrWillBeMember<StyleRuleBase>> CSSParserImpl::consumeRuleLi
             if (PassRefPtrWillBeRawPtr<StyleRuleBase> rule = consumeAtRule(range, allowedRules))
                 result.append(rule);
             break;
+        case CDOToken:
+        case CDCToken:
+            if (ruleListType == TopLevelRuleList) {
+                range.consume();
+                break;
+            }
+            // fallthrough
         default:
-            // FIXME: TopLevelRuleList should skip <CDO-token> and <CDC-token>
             if (PassRefPtrWillBeRawPtr<StyleRuleBase> rule = consumeQualifiedRule(range, allowedRules))
                 result.append(rule);
             break;