Convert raw pointer members to references.

This is now allowed by the style guide. The benefit is to lock down
reassignment and make nullability clearer.

Test: launch_cvd
Change-Id: I180e5d8ff471306eb63fdae1004b3d329468918a
diff --git a/host/commands/secure_env/keymaster_responder.h b/host/commands/secure_env/keymaster_responder.h
index 1fc662e..f8fb6ec 100644
--- a/host/commands/secure_env/keymaster_responder.h
+++ b/host/commands/secure_env/keymaster_responder.h
@@ -21,11 +21,11 @@
 
 class KeymasterResponder {
 private:
-  cuttlefish::KeymasterChannel* channel_;
-  keymaster::AndroidKeymaster* keymaster_;
+  cuttlefish::KeymasterChannel& channel_;
+  keymaster::AndroidKeymaster& keymaster_;
 public:
-  KeymasterResponder(cuttlefish::KeymasterChannel* channel,
-                     keymaster::AndroidKeymaster* keymaster);
+  KeymasterResponder(cuttlefish::KeymasterChannel& channel,
+                     keymaster::AndroidKeymaster& keymaster);
 
   bool ProcessMessage();
 };