Added crypto random-number generator

base/rand_util.h

Index: base/rand_util.h
diff --git a/base/rand_util.h b/base/rand_util.h
index 82e548b82923d45d0c805be920981528e0c60887..51f7f7ffbfb4d9770c038803e9604a35bba459f5 100644
--- a/base/rand_util.h
+++ b/base/rand_util.h
@@ -33,12 +33,16 @@ BASE_EXPORT double RandDouble();
 // the range [0, 1). Thread-safe.
 BASE_EXPORT double BitsToOpenEndedUnitInterval(uint64 bits);
 
-// Fills |output_length| bytes of |output| with cryptographically strong random
-// data.
+// Fills |output_length| bytes of |output| with random data.
+// Note: The random data is cryptographically secure, but use the RNG in crypto/
+// for security-sensitive purposes instead of this function.
 BASE_EXPORT void RandBytes(void* output, size_t output_length);
 
-// Fills a string of length |length| with with cryptographically strong random
-// data and returns it.  |length| should be nonzero.
+// Fills a string of length |length| with with random data and returns it.
+// |length| should be nonzero.
+//
+// Note: The random data is cryptographically secure, but use the RNG in crypto/
+// for security-sensitive purposes instead of this function.
 //
 // Note that this is a variation of |RandBytes| with a different return type.
 BASE_EXPORT std::string RandBytesAsString(size_t length);