Expose crypto.getRandomValues() to workers.

Source/wtf/CryptographicallyRandomNumber.h

 /*
  * Copyright (C) 2008 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  *
  * 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 16 matching lines @@
 #define WTF_CryptographicallyRandomNumber_h
 
 #include <stdint.h>
 
 #include "wtf/WTFExport.h"
 
 namespace WTF {
 
 typedef void (*RandomNumberSource)(unsigned char*, size_t);
 
+// The RandomNumberSource function MUST be threadsafe.
 WTF_EXPORT void setRandomSource(RandomNumberSource);
 
+// These functions are threadsafe.
 WTF_EXPORT uint32_t cryptographicallyRandomNumber();
 WTF_EXPORT void cryptographicallyRandomValues(void* buffer, size_t length);
 
 }
 
 using WTF::cryptographicallyRandomNumber;
 using WTF::cryptographicallyRandomValues;
 
 #endif