components: Cleanup class/struct fwd declarations

components/proximity_auth/remote_device_life_cycle.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef COMPONENTS_PROXIMITY_AUTH_REMOTE_DEVICE_LIFE_CYCLE_H
 #define COMPONENTS_PROXIMITY_AUTH_REMOTE_DEVICE_LIFE_CYCLE_H
 
 #include "base/macros.h"
 #include "components/proximity_auth/remote_device.h"
 
 namespace proximity_auth {
 
-class Authenticator;
 class Messenger;
-class ConnectionFinder;
 
 // Controls the life cycle of connecting and authenticating to a remote device.
 // After the life cycle is started, it can be in the following states:
 //   FINDING_CONNECTION:
 //       Continuiously attempts to create a connection to the remote device.
 //       After connecting, transitions to the AUTHENTICATING state.
 //   AUTHENTICATING:
 //       Verifies that the connected device has the correct credentials. On
 //       success, transitions to SECURE_CHANNEL_ESTABLISHED; otherwise,
 //       transitions to AUTHENTICATION_FAILED.
@@ skipping 44 matching lines @@
   // Adds an observer.
   virtual void AddObserver(Observer* observer) = 0;
 
   // Removes an observer.
   virtual void RemoveObserver(Observer* observer) = 0;
 };
 
 }  // namespace proximity_auth
 
 #endif  // COMPONENTS_PROXIMITY_AUTH_REMOTE_DEVICE_LIFE_CYCLE_H