relnote: initialize client_common_set_hashes and

client_cached_cert_hashes to nullptr in default
QuicCompressedCertsCache::UncompressedCerts constructor.

BUG=716026

Review-Url: https://codereview.chromium.org/2848883006
Cr-Commit-Position: refs/heads/master@{#468220}

net/quic/core/crypto/quic_compressed_certs_cache.cc

@@ -19,7 +19,9 @@ inline void hash_combine(uint64_t* seed, const uint64_t& val) {
 }  // namespace
 
 QuicCompressedCertsCache::UncompressedCerts::UncompressedCerts()
-    : chain(nullptr) {}
+    : chain(nullptr),
+      client_common_set_hashes(nullptr),
+      client_cached_cert_hashes(nullptr) {}
 
 QuicCompressedCertsCache::UncompressedCerts::UncompressedCerts(
     const QuicReferenceCountedPointer<ProofSource::Chain>& chain,