Hook up ProximityAuthSystem in EasyUnlockService.

components/proximity_auth/unlock_manager.h

Index: components/proximity_auth/unlock_manager.h
diff --git a/components/proximity_auth/unlock_manager.h b/components/proximity_auth/unlock_manager.h
index 88f6f276e26e60526e86db2453fdf6b84fe4a4f3..b3a7d69acd5eb79d854f0b50f1f9269acfb73316 100644
--- a/components/proximity_auth/unlock_manager.h
+++ b/components/proximity_auth/unlock_manager.h
@@ -62,7 +62,6 @@ class UnlockManager : public MessengerObserver,
   // Called when the life cycle's state changes.
   void OnLifeCycleStateChanged();
 
- protected:
   // Called when the user pod is clicked for an authentication attempt of type
   // |auth_type|.
   // Exposed for testing.
@@ -135,6 +134,11 @@ class UnlockManager : public MessengerObserver,
   RemoteScreenlockState GetScreenlockStateFromRemoteUpdate(
       RemoteStatusUpdate update);
 
+  // Returns the Messenger instance associated with |life_cycle_|. This function
+  // will return nullptr if |life_cycle_| is not set or the remote device is not
+  // yet authenticated.
+  Messenger* GetMessenger();
+
   // Whether |this| manager is being used for sign-in or session unlock.
   const ScreenlockType screenlock_type_;
 
@@ -146,12 +150,6 @@ class UnlockManager : public MessengerObserver,
   // expcted to outlive |this| instance.
   RemoteDeviceLifeCycle* life_cycle_;
 
-  // The messenger used to communicate with the remote device once a secure
-  // channel
-  // is established. Null if no secure channel has been established yet. Not
-  // owned, and expected to outlive |this| instance.
-  Messenger* messenger_;
-
   // Tracks whether the remote device is currently in close enough proximity to
   // the local device to allow unlocking.
   scoped_ptr<ProximityMonitor> proximity_monitor_;