Add a Clone method to ProofVerifyDetails to allow for the proof verify

net/quic/crypto/proof_verifier.h

Index: net/quic/crypto/proof_verifier.h
diff --git a/net/quic/crypto/proof_verifier.h b/net/quic/crypto/proof_verifier.h
index 83f7c4366fdb7faabc3223569702fb6b7ec4bd65..7ddd8f7047e306110ee9589a7848c7a8993a0cac 100644
--- a/net/quic/crypto/proof_verifier.h
+++ b/net/quic/crypto/proof_verifier.h
@@ -20,6 +20,10 @@ namespace net {
 class NET_EXPORT_PRIVATE ProofVerifyDetails {
  public:
   virtual ~ProofVerifyDetails() {}
+
+  // Returns an new ProofVerifyDetails object with the same contents
+  // as this one.
+  virtual ProofVerifyDetails* Clone() const = 0;
 };
 
 // ProofVerifyContext is an abstract class that acts as a container for any