Fix null dereference on MemoryCache.

third_party/WebKit/Source/core/fetch/CSSStyleSheetResource.h

Index: third_party/WebKit/Source/core/fetch/CSSStyleSheetResource.h
diff --git a/third_party/WebKit/Source/core/fetch/CSSStyleSheetResource.h b/third_party/WebKit/Source/core/fetch/CSSStyleSheetResource.h
index eafa35dcbb4955ae86baa50933466ba8eda44493..411e7e102fc2a2a587389ff4e3bd83f55ad9bc71 100644
--- a/third_party/WebKit/Source/core/fetch/CSSStyleSheetResource.h
+++ b/third_party/WebKit/Source/core/fetch/CSSStyleSheetResource.h
@@ -26,6 +26,7 @@
 #ifndef CSSStyleSheetResource_h
 #define CSSStyleSheetResource_h
 
+#include "core/CoreExport.h"
 #include "core/fetch/ResourcePtr.h"
 #include "core/fetch/StyleSheetResource.h"
 #include "platform/heap/Handle.h"
@@ -38,11 +39,12 @@ class ResourceClient;
 class ResourceFetcher;
 class StyleSheetContents;
 
-class CSSStyleSheetResource final : public StyleSheetResource {
+class CORE_EXPORT CSSStyleSheetResource final : public StyleSheetResource {
 public:
     enum class MIMETypeCheck { Strict, Lax };
 
     static ResourcePtr<CSSStyleSheetResource> fetch(FetchRequest&, ResourceFetcher*);
+    static ResourcePtr<CSSStyleSheetResource> createForTest(const ResourceRequest&, const String& charset);
 
     ~CSSStyleSheetResource() override;
     DECLARE_VIRTUAL_TRACE();