Fix null dereference on MemoryCache.

third_party/WebKit/Source/core/css/CSSPropertyMetadata.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 CSSPropertyMetadata_h
 #define CSSPropertyMetadata_h
 
 #include "core/CSSPropertyNames.h"
+#include "core/CoreExport.h"
 #include "wtf/Allocator.h"
 
 namespace blink {
 
-class CSSPropertyMetadata {
+class CORE_EXPORT CSSPropertyMetadata {
     STATIC_ONLY(CSSPropertyMetadata);
 public:
     static bool isEnabledProperty(CSSPropertyID);
     static bool isInterpolableProperty(CSSPropertyID);
     static bool isInheritedProperty(CSSPropertyID);
 
     static void filterEnabledCSSPropertiesIntoVector(const CSSPropertyID*, size_t length, Vector<CSSPropertyID>&);
 };
 
 } // namespace blink
 
 #endif // CSSPropertyMetadata