[CrOS Tether] Create KeepAliveScheduler, a class which schedules keep-alive tickles to be sent to a…

chromeos/components/tether/keep_alive_operation.h

 // Copyright 2017 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 CHROMEOS_COMPONENTS_TETHER_KEEP_ALIVE_OPERATION_H_
 #define CHROMEOS_COMPONENTS_TETHER_KEEP_ALIVE_OPERATION_H_
 
+#include "base/observer_list.h"
 #include "chromeos/components/tether/message_transfer_operation.h"
 
 namespace chromeos {
 
 namespace tether {
 
 class BleConnectionManager;
 
 // Operation which sends a keep-alive message to a tether host.
-// TODO(khorimoto/hansberry): Consider changing protocol to receive a
-//                            DeviceStatus update after sending the
-//                            KeepAliveTickle message.
+// TODO(khorimoto/hansberry): Change protocol to receive a DeviceStatus update
+//                            after sending the KeepAliveTickle message.
 class KeepAliveOperation : public MessageTransferOperation {
  public:
   class Factory {
    public:
     static std::unique_ptr<KeepAliveOperation> NewInstance(
         const cryptauth::RemoteDevice& device_to_connect,
         BleConnectionManager* connection_manager);
 
     static void SetInstanceForTesting(Factory* factory);
 
    protected:
     virtual std::unique_ptr<KeepAliveOperation> BuildInstance(
-        const cryptauth::RemoteDevice& devices_to_connect,
+        const cryptauth::RemoteDevice& device_to_connect,
         BleConnectionManager* connection_manager);
 
    private:
     static Factory* factory_instance_;
   };
 
+  class Observer {
+   public:
+    // TODO(khorimoto): This function should take a DeviceStatus once there is
+    //                  keep-alive tickle response.
+    virtual void OnOperationFinished() = 0;
+  };
+
   KeepAliveOperation(const cryptauth::RemoteDevice& device_to_connect,
                      BleConnectionManager* connection_manager);
   ~KeepAliveOperation() override;
 
   void AddObserver(Observer* observer);
   void RemoveObserver(Observer* observer);
 
  protected:
   // MessageTransferOperation:
   void OnDeviceAuthenticated(
       const cryptauth::RemoteDevice& remote_device) override;
+  void OnOperationFinished() override;
   MessageType GetMessageTypeForConnection() override;
 
  private:
   friend class KeepAliveOperationTest;
 
+  base::ObserverList<Observer> observer_list_;
+  bool has_authenticated_;
+
   DISALLOW_COPY_AND_ASSIGN(KeepAliveOperation);
 };
 
 }  // namespace tether
 
 }  // namespace chromeos
 
 #endif  // CHROMEOS_COMPONENTS_TETHER_KEEP_ALIVE_OPERATION_H_