Disable the thread-safe MQ parser for main thread

Source/core/css/parser/BisonCSSParser-in.cpp

Index: Source/core/css/parser/BisonCSSParser-in.cpp
diff --git a/Source/core/css/parser/BisonCSSParser-in.cpp b/Source/core/css/parser/BisonCSSParser-in.cpp
index 1bd084d72375943a7a35fee7d38c69982bc969b6..7a655c2c3545718b6fed1bbba0bfc2ae41f447d1 100644
--- a/Source/core/css/parser/BisonCSSParser-in.cpp
+++ b/Source/core/css/parser/BisonCSSParser-in.cpp
@@ -1212,6 +1212,19 @@ bool BisonCSSParser::parseDeclaration(MutableStylePropertySet* declaration, cons
     return ok;
 }
 
+PassRefPtrWillBeRawPtr<MediaQuerySet> BisonCSSParser::parseMediaQueryList(const String& string)
+{
+    ASSERT(!m_mediaList);
+
+    // can't use { because tokenizer state switches from mediaquery to initial state when it sees { token.
+    // instead insert one " " (which is caught by maybe_space in CSSGrammar.y)
+    setupParser("@-internal-medialist ", string, "");
+    cssyyparse(this);
+
+    ASSERT(m_mediaList);
+    return m_mediaList.release();
+}
+
 static inline void filterProperties(bool important, const WillBeHeapVector<CSSProperty, 256>& input, WillBeHeapVector<CSSProperty, 256>& output, size_t& unusedEntries, BitArray<numCSSProperties>& seenProperties)
 {
     // Add properties in reverse order so that highest priority definitions are reached first. Duplicate definitions can then be ignored when found.