Null check font family name in createFontFamilyValue

third_party/WebKit/Source/core/css/CSSValuePool.cpp

 /*
  * Copyright (C) 2011, 2012 Apple 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 110 matching lines @@
     }
 }
 
 PassRefPtrWillBeRawPtr<CSSPrimitiveValue> CSSValuePool::createValue(const Length& value, const ComputedStyle& style)
 {
     return CSSPrimitiveValue::create(value, style.effectiveZoom());
 }
 
 PassRefPtrWillBeRawPtr<CSSFontFamilyValue> CSSValuePool::createFontFamilyValue(const String& familyName)
 {
+    if (familyName.isNull())
+        return CSSFontFamilyValue::create(familyName);
     RefPtrWillBeMember<CSSFontFamilyValue>& value = m_fontFamilyValueCache.add(familyName, nullptr).storedValue->value;
     if (!value)
         value = CSSFontFamilyValue::create(familyName);
     return value;
 }
 
 PassRefPtrWillBeRawPtr<CSSValueList> CSSValuePool::createFontFaceValue(const AtomicString& string)
 {
     // Just wipe out the cache and start rebuilding if it gets too big.
     const unsigned maximumFontFaceCacheSize = 128;
@@ skipping 23 matching lines @@
     visitor->trace(m_colorBlack);
     visitor->trace(m_pixelValueCache);
     visitor->trace(m_percentValueCache);
     visitor->trace(m_numberValueCache);
     visitor->trace(m_fontFaceValueCache);
     visitor->trace(m_fontFamilyValueCache);
 #endif
 }
 
 } // namespace blink