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

src/utils/random-number-generator.cc

 // 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
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 //       disclaimer in the documentation and/or other materials provided
@@ skipping 64 matching lines @@
     fclose(fp);
     if (n == 1) {
       SetSeed(seed);
       return;
     }
   }
 
   // We cannot assume that random() or rand() were seeded
   // properly, so instead of relying on random() or rand(),
   // we just seed our PRNG using timing data as fallback.
+  // This is weak entropy, 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
   int64_t seed = Time::NowFromSystemTime().ToInternalValue() << 24;
   seed ^= TimeTicks::HighResNow().ToInternalValue() << 16;
   seed ^= TimeTicks::Now().ToInternalValue() << 8;
   SetSeed(seed);
 }
 
 
 int RandomNumberGenerator::NextInt(int max) {
   ASSERT_LE(0, max);
 
@@ skipping 32 matching lines @@
   seed_ = seed;
   return static_cast<int>(seed >> (48 - bits));
 }
 
 
 void RandomNumberGenerator::SetSeed(int64_t seed) {
   seed_ = (seed ^ kMultiplier) & kMask;
 }
 
 } }  // namespace v8::internal