Pseudo element selectors in compound selector lists are invalid.

third_party/WebKit/Source/core/css/parser/CSSSelectorParser.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CSSSelectorParser_h
 #define CSSSelectorParser_h
 
 #include "core/CoreExport.h"
 #include "core/css/parser/CSSParserSelector.h"
 #include "core/css/parser/CSSParserTokenRange.h"
@@ skipping 40 matching lines @@
     const AtomicString& defaultNamespace() const;
     const AtomicString& determineNamespace(const AtomicString& prefix);
     void prependTypeSelectorIfNeeded(const AtomicString& namespacePrefix, const AtomicString& elementName, CSSParserSelector*);
     void rewriteSpecifiersWithElementNameForCustomPseudoElement(const QualifiedName& tag, CSSParserSelector*, bool tagIsImplicit);
     void rewriteSpecifiersWithElementNameForContentPseudoElement(const QualifiedName& tag, CSSParserSelector*, bool tagIsImplicit);
     static PassOwnPtr<CSSParserSelector> addSimpleSelectorToCompound(PassOwnPtr<CSSParserSelector> compoundSelector, PassOwnPtr<CSSParserSelector> simpleSelector);
 
     const CSSParserContext& m_context;
     RawPtrWillBeMember<StyleSheetContents> m_styleSheet; // FIXME: Should be const
 
-    bool m_failedParsing;
+    bool m_failedParsing = false;
+    bool m_disallowPseudoElements = false;
+
+    class DisallowPseudoElementsScope {
+        STACK_ALLOCATED();
+        WTF_MAKE_NONCOPYABLE(DisallowPseudoElementsScope);
+    public:
+        DisallowPseudoElementsScope(CSSSelectorParser* parser)
+            : m_parser(parser), m_wasDisallowed(m_parser->m_disallowPseudoElements)
+        {
+            m_parser->m_disallowPseudoElements = true;
+        }
+
+        ~DisallowPseudoElementsScope()
+        {
+            m_parser->m_disallowPseudoElements = m_wasDisallowed;
+        }
+
+    private:
+        CSSSelectorParser* m_parser;
+        bool m_wasDisallowed;
+    };
 };
 
 } // namespace
 
 #endif // CSSSelectorParser_h