[StunRequest] Remove Construct and Prepare methods.

Construction in StunRequest and derived classes now happens in
the ctor.

Bug: none
Change-Id: I803f6fd2b6d0ac1d9426304d1e1de10dec855eed
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/264942
Commit-Queue: Tomas Gunnarsson <tommi@webrtc.org>
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#37126}
diff --git a/p2p/base/stun_request.h b/p2p/base/stun_request.h
index 94fc98f..c6d1076 100644
--- a/p2p/base/stun_request.h
+++ b/p2p/base/stun_request.h
@@ -114,14 +114,7 @@
  protected:
   friend class StunRequestManager;
 
-  // Causes our wrapped StunMessage to be Prepared.
-  // Only called by StunRequestManager.
-  // TODO(tommi): get rid of this (see cc file).
-  void Construct();
-
-  // Fills in a request object to be sent.  Note that request's transaction ID
-  // will already be set and cannot be changed.
-  virtual void Prepare(StunMessage* message) {}
+  StunMessage* mutable_msg() { return msg_.get(); }
 
   // Called when the message receives a response or times out.
   virtual void OnResponse(StunMessage* response) {}