[rng] improve RNG seed.

src/base/utils/random-number-generator.cc

Index: src/base/utils/random-number-generator.cc
diff --git a/src/base/utils/random-number-generator.cc b/src/base/utils/random-number-generator.cc
index ff428402b6b7c92faf4dab6cb8569458606ade32..3a6f2c63cf96c845802f1e0ae0d86a161e3c38fb 100644
--- a/src/base/utils/random-number-generator.cc
+++ b/src/base/utils/random-number-generator.cc
@@ -124,10 +124,10 @@ int RandomNumberGenerator::Next(int bits) {
 
 
 void RandomNumberGenerator::SetSeed(int64_t seed) {
-  if (seed == 0) seed = 1;
   initial_seed_ = seed;
   state0_ = MurmurHash3(bit_cast<uint64_t>(seed));
-  state1_ = MurmurHash3(state0_);
+  state1_ = MurmurHash3(~state0_);
+  CHECK(state0_ != 0 || state1_ != 0);
 }