chrome: Add out-of-line copy ctors for complex classes.

chrome/renderer/media/cast_transport_sender_ipc.h

Index: chrome/renderer/media/cast_transport_sender_ipc.h
diff --git a/chrome/renderer/media/cast_transport_sender_ipc.h b/chrome/renderer/media/cast_transport_sender_ipc.h
index af66c03609469c8190a812b3a81b6d2ab4119d2e..5e56e423ebee02ea0c75d5a328135bdb0d70ded9 100644
--- a/chrome/renderer/media/cast_transport_sender_ipc.h
+++ b/chrome/renderer/media/cast_transport_sender_ipc.h
@@ -74,6 +74,7 @@ class CastTransportSenderIPC
  private:
   struct ClientCallbacks {
     ClientCallbacks();
+    ClientCallbacks(const ClientCallbacks& other);
     ~ClientCallbacks();
 
     media::cast::RtcpCastMessageCallback cast_message_cb;