Fix an MQ parsing related crash

Source/core/css/CSSParserValuesTest.cpp

Index: Source/core/css/CSSParserValuesTest.cpp
diff --git a/Source/core/css/CSSParserValuesTest.cpp b/Source/core/css/CSSParserValuesTest.cpp
index 41ad43ccc2b812e275c378e243af80ca9036cd92..7e4341189fea4e4a767ca8f5ceb2b8c4307406e0 100644
--- a/Source/core/css/CSSParserValuesTest.cpp
+++ b/Source/core/css/CSSParserValuesTest.cpp
@@ -84,4 +84,17 @@ TEST(CSSParserValuesTest, EqualIgnoringCase16BitsString)
     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