Remove more trampoline functions from ChannelManager

Bug: webrtc:13931
Change-Id: I3a1b48aeffd91ee6abaf78eb1ec69c1653b210e6
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/262640
Reviewed-by: Florent Castelli <orphis@webrtc.org>
Commit-Queue: Harald Alvestrand <hta@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#36898}
diff --git a/pc/peer_connection_factory.h b/pc/peer_connection_factory.h
index ff3d515..917f054 100644
--- a/pc/peer_connection_factory.h
+++ b/pc/peer_connection_factory.h
@@ -120,6 +120,8 @@
     return context_->field_trials();
   }
 
+  cricket::MediaEngineInterface* media_engine() const;
+
  protected:
   // Constructor used by the static Create() method. Modifies the dependencies.
   PeerConnectionFactory(rtc::scoped_refptr<ConnectionContext> context,