Fix an MQ parsing related crash

Source/core/css/CSSParserValuesTest.cpp

 /*
  * Copyright 2013, Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 66 matching lines @@
     CSSParserString cssParserString;
     cssParserString.init(string16bit, 0, string16bit.length());
 
     ASSERT_TRUE(cssParserString.equalIgnoringCase("shadow"));
     ASSERT_TRUE(cssParserString.equalIgnoringCase("ShaDow"));
     ASSERT_FALSE(cssParserString.equalIgnoringCase("shadow-all"));
     ASSERT_FALSE(cssParserString.equalIgnoringCase("sha"));
     ASSERT_FALSE(cssParserString.equalIgnoringCase("abCD"));
 }
 
+TEST(CSSParserValuesTest, CSSParserValuelistClear)
+{
+    CSSParserValueList list;
+    for (int i = 0; i < 3; ++i) {
+        CSSParserValue value;
+        value.setFromNumber(3);
+        list.addValue(value);
+    }
+    list.clear();
+    ASSERT_FALSE(list.size());
+    ASSERT_FALSE(list.currentIndex());
+}
+
 } // namespace