Rename [Un]SubscribeClose event subscription methods for clarity.

This is following up on a discussion here:
https://webrtc-review.googlesource.com/c/src/+/318061

Bug: none
Change-Id: Idb572ca6d0aad8d791eb6ba80dc0f48292f9f244
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/318883
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Commit-Queue: Tomas Gunnarsson <tommi@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#40698}
diff --git a/rtc_base/async_packet_socket.h b/rtc_base/async_packet_socket.h
index ad9a79e..0d3ceb9 100644
--- a/rtc_base/async_packet_socket.h
+++ b/rtc_base/async_packet_socket.h
@@ -110,9 +110,10 @@
   virtual void SetError(int error) = 0;
 
   // Register a callback to be called when the socket is closed.
-  void SubscribeClose(const void* removal_tag,
-                      std::function<void(AsyncPacketSocket*, int)> callback);
-  void UnsubscribeClose(const void* removal_tag);
+  void SubscribeCloseEvent(
+      const void* removal_tag,
+      std::function<void(AsyncPacketSocket*, int)> callback);
+  void UnsubscribeCloseEvent(const void* removal_tag);
 
   // Emitted each time a packet is read. Used only for UDP and
   // connected TCP sockets.