Document that its the job of the embedder to provide strong entropy for seeding the PRNG.

src/utils/random-number-generator.h

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 24 matching lines @@
 
 // -----------------------------------------------------------------------------
 // RandomNumberGenerator
 //
 // This class is used to generate a stream of pseudorandom numbers. The class
 // uses a 48-bit seed, which is modified using a linear congruential formula.
 // (See Donald Knuth, The Art of Computer Programming, Volume 3, Section 3.2.1.)
 // If two instances of RandomNumberGenerator are created with the same seed, and
 // the same sequence of method calls is made for each, they will generate and
 // return identical sequences of numbers.
+// This class uses (probably) weak entropy by default, but it's sufficient,
+// because it is the responsibility of the embedder to install an entropy source
+// using v8::V8::SetEntropySource(), which provides reasonable entropy, see:
+// https://code.google.com/p/v8/issues/detail?id=2905
 // This class is neither reentrant nor threadsafe.
 
 class RandomNumberGenerator V8_FINAL {
  public:
   // EntropySource is used as a callback function when V8 needs a source of
   // entropy.
   typedef bool (*EntropySource)(unsigned char* buffer, size_t buflen);
   static void SetEntropySource(EntropySource entropy_source);
 
   RandomNumberGenerator();
@@ skipping 42 matching lines @@
 
   int Next(int bits) V8_WARN_UNUSED_RESULT;
   void SetSeed(int64_t seed);
 
   int64_t seed_;
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_UTILS_RANDOM_NUMBER_GENERATOR_H_