[webcrypto] Fix TODO regarding asynchronous completion of crypto operations.

Source/core/platform/CryptoResult.h

Index: Source/core/platform/CryptoResult.h
diff --git a/Source/core/platform/CryptoResult.h b/Source/core/platform/CryptoResult.h
index 45aaef5945b57f7568d085f1099b99a87050a7ad..0ba22215c9af38d7dfca6a2c984fa45af6c1b58c 100644
--- a/Source/core/platform/CryptoResult.h
+++ b/Source/core/platform/CryptoResult.h
@@ -32,12 +32,12 @@
 #define CryptoResult_h
 
 #include "public/platform/WebCrypto.h"
-#include "wtf/ThreadSafeRefCounted.h"
+#include "wtf/RefCounted.h"
 
 namespace WebCore {
 
 // Receives notification of completion of the crypto operation.
-class CryptoResult : public ThreadSafeRefCounted<CryptoResult> {
+class CryptoResult : public RefCounted<CryptoResult> {
 public:
     virtual ~CryptoResult() { }