base: Fix the p2p AgentSession registration logic

The refactoring in commit 4efb90a ended
up breaking p2p support entirely. Instead of registering an AgentSession
on the connection, we would register an AgentMessageTransmitter.

lib/base/session.vala

@@ -150,6 +150,11 @@ namespace Frida {
 		public signal void new_candidates (string[] candidate_sdps);
 		public signal void candidate_gathering_done ();
 
+		public weak AgentSession agent_session {
+			get;
+			construct;
+		}
+
 		public uint persist_timeout {
 			get;
 			construct;
@@ -198,8 +203,10 @@ namespace Frida {
 			INTERRUPTED
 		}
 
-		public AgentMessageTransmitter (uint persist_timeout, MainContext frida_context, MainContext dbus_context) {
+		public AgentMessageTransmitter (AgentSession agent_session, uint persist_timeout, MainContext frida_context,
+				MainContext dbus_context) {
 			Object (
+				agent_session: agent_session,
 				persist_timeout: persist_timeout,
 				frida_context: frida_context,
 				dbus_context: dbus_context
@@ -500,8 +507,7 @@ namespace Frida {
 				nice_connection.on_closed.connect (on_nice_connection_closed);
 
 				try {
-					nice_registration_id = nice_connection.register_object (ObjectPath.AGENT_SESSION,
-						(AgentSession) this);
+					nice_registration_id = nice_connection.register_object (ObjectPath.AGENT_SESSION, agent_session);
 				} catch (IOError io_error) {
 					assert_not_reached ();
 				}

lib/payload/base-agent-session.vala

@@ -50,7 +50,7 @@ namespace Frida {
 			script_engine.message_from_script.connect (on_message_from_script);
 			script_engine.message_from_debugger.connect (on_message_from_debugger);
 
-			transmitter = new AgentMessageTransmitter (persist_timeout, frida_context, dbus_context);
+			transmitter = new AgentMessageTransmitter (this, persist_timeout, frida_context, dbus_context);
 			transmitter.closed.connect (on_transmitter_closed);
 			transmitter.new_candidates.connect (on_transmitter_new_candidates);
 			transmitter.candidate_gathering_done.connect (on_transmitter_candidate_gathering_done);

src/barebone/barebone-host-session.vala

@@ -343,7 +343,7 @@ namespace Frida {
 			assert (frida_context != null);
 			assert (dbus_context != null);
 
-			transmitter = new AgentMessageTransmitter (persist_timeout, frida_context, dbus_context);
+			transmitter = new AgentMessageTransmitter (this, persist_timeout, frida_context, dbus_context);
 			transmitter.closed.connect (on_transmitter_closed);
 			transmitter.new_candidates.connect (on_transmitter_new_candidates);
 			transmitter.candidate_gathering_done.connect (on_transmitter_candidate_gathering_done);