[CrOS Tether] Create TetherDisconnector, which disconnects from active tethering sessions.

chromeos/components/tether/disconnect_tethering_operation.cc

Index: chromeos/components/tether/disconnect_tethering_operation.cc
diff --git a/chromeos/components/tether/disconnect_tethering_operation.cc b/chromeos/components/tether/disconnect_tethering_operation.cc
index f8ba990672e9dda82e45a0a223881292b210d2c2..72b2218b0ade078a83bc2804f0d1bd6ad484195f 100644
--- a/chromeos/components/tether/disconnect_tethering_operation.cc
+++ b/chromeos/components/tether/disconnect_tethering_operation.cc
@@ -48,6 +48,7 @@ DisconnectTetheringOperation::DisconnectTetheringOperation(
     : MessageTransferOperation(
           std::vector<cryptauth::RemoteDevice>{device_to_connect},
           connection_manager),
+      device_id_(device_to_connect.GetDeviceId()),
       has_authenticated_(false) {}
 
 DisconnectTetheringOperation::~DisconnectTetheringOperation() {}
@@ -60,6 +61,13 @@ void DisconnectTetheringOperation::RemoveObserver(Observer* observer) {
   observer_list_.RemoveObserver(observer);
 }
 
+void DisconnectTetheringOperation::NotifyObserversOperationFinished(
+    bool success) {
+  for (auto& observer : observer_list_) {
+    observer.OnOperationFinished(device_id_, success);
+  }
+}
+
 void DisconnectTetheringOperation::OnDeviceAuthenticated(
     const cryptauth::RemoteDevice& remote_device) {
   DCHECK(remote_devices().size() == 1u && remote_devices()[0] == remote_device);
@@ -71,9 +79,7 @@ void DisconnectTetheringOperation::OnDeviceAuthenticated(
 }
 
 void DisconnectTetheringOperation::OnOperationFinished() {
-  for (auto& observer : observer_list_) {
-    observer.OnOperationFinished(has_authenticated_);
-  }
+  NotifyObserversOperationFinished(has_authenticated_);
 }
 
 MessageType DisconnectTetheringOperation::GetMessageTypeForConnection() {