Fix race at GCInfo::index.

Source/platform/heap/Visitor.h

Index: Source/platform/heap/Visitor.h
diff --git a/Source/platform/heap/Visitor.h b/Source/platform/heap/Visitor.h
index cb85371e7f8c2c1347d5740549ca466a4c739794..1a50d167289ab6dbd5e7863c176fbfc1777adecb 100644
--- a/Source/platform/heap/Visitor.h
+++ b/Source/platform/heap/Visitor.h
@@ -42,7 +42,6 @@
 #include "wtf/HashMap.h"
 #include "wtf/HashTraits.h"
 #include "wtf/InstanceCounter.h"
-#include "wtf/Threading.h"
 #include "wtf/TypeTraits.h"
 #include "wtf/text/WTFString.h"
 
@@ -387,11 +386,9 @@ private:
 
 template<typename T>
 struct TypenameStringTrait {
-    // This method is not thread safe.
-    static const String& get()
+    static const String get()
     {
-        AtomicallyInitializedStaticReference(AtomicString, typenameString, new AtomicString(WTF::extractTypeNameFromFunctionName(WTF::extractNameFunction<T>())));
-        return typenameString;
+        return WTF::extractTypeNameFromFunctionName(WTF::extractNameFunction<T>());
     }
 };