[Cast Channel] Add support for nonce challenge to Cast channel authentication.

extensions/browser/api/cast_channel/cast_socket.h

Index: extensions/browser/api/cast_channel/cast_socket.h
diff --git a/extensions/browser/api/cast_channel/cast_socket.h b/extensions/browser/api/cast_channel/cast_socket.h
index 78a7bb0d5d8fa791e98b352b45acaa448e180341..9423a48940e9c0daa6feeed05f8ded269f5d475a 100644
--- a/extensions/browser/api/cast_channel/cast_socket.h
+++ b/extensions/browser/api/cast_channel/cast_socket.h
@@ -18,6 +18,7 @@
 #include "base/timer/timer.h"
 #include "extensions/browser/api/api_resource.h"
 #include "extensions/browser/api/api_resource_manager.h"
+#include "extensions/browser/api/cast_channel/cast_auth_util.h"
 #include "extensions/browser/api/cast_channel/cast_socket.h"
 #include "extensions/browser/api/cast_channel/cast_transport.h"
 #include "extensions/common/api/cast_channel.h"
@@ -156,6 +157,18 @@ class CastSocketImpl : public CastSocket {
                  const scoped_refptr<Logger>& logger,
                  uint64_t device_capabilities);
 
+  // For test-only.
+  // This constructor allows for setting a custom AuthContext.
+  CastSocketImpl(const std::string& owner_extension_id,
+                 const net::IPEndPoint& ip_endpoint,
+                 ChannelAuthType channel_auth,
+                 net::NetLog* net_log,
+                 const base::TimeDelta& connect_timeout,
+                 bool keep_alive,
+                 const scoped_refptr<Logger>& logger,
+                 uint64_t device_capabilities,
+                 const AuthContext& auth_context);
+
   // Ensures that the socket is closed.
   ~CastSocketImpl() override;
 
@@ -322,6 +335,9 @@ class CastSocketImpl : public CastSocket {
   // certificate is not yet fetched.
   scoped_refptr<net::X509Certificate> peer_cert_;
 
+  // The challenge context for the current connection.
+  const AuthContext auth_context_;
+
   // Reply received from the receiver to a challenge request.
   std::unique_ptr<CastMessage> challenge_reply_;