(Fix landed) Revert of [CrOS Tether] Create HostScanCache, which caches scan results and inserts...

chromeos/components/tether/tether_host_response_recorder.cc

Index: chromeos/components/tether/tether_host_response_recorder.cc
diff --git a/chromeos/components/tether/tether_host_response_recorder.cc b/chromeos/components/tether/tether_host_response_recorder.cc
index c284ed9103c5b8687d4dd466bb605ae3c04e2d8d..7012fa67009c47235e8de8c8c90a70e82593526e 100644
--- a/chromeos/components/tether/tether_host_response_recorder.cc
+++ b/chromeos/components/tether/tether_host_response_recorder.cc
@@ -26,14 +26,6 @@
 
 TetherHostResponseRecorder::~TetherHostResponseRecorder() {}
 
-void TetherHostResponseRecorder::AddObserver(Observer* observer) {
-  observer_list_.AddObserver(observer);
-}
-
-void TetherHostResponseRecorder::RemoveObserver(Observer* observer) {
-  observer_list_.RemoveObserver(observer);
-}
-
 void TetherHostResponseRecorder::RecordSuccessfulTetherAvailabilityResponse(
     const cryptauth::RemoteDevice& remote_device) {
   AddRecentResponse(remote_device.GetDeviceId(),
@@ -47,10 +39,8 @@
 
 void TetherHostResponseRecorder::RecordSuccessfulConnectTetheringResponse(
     const cryptauth::RemoteDevice& remote_device) {
-  if (AddRecentResponse(remote_device.GetDeviceId(),
-                        prefs::kMostRecentConnectTetheringResponderIds)) {
-    NotifyObserversPreviouslyConnectedHostIdsChanged();
-  }
+  AddRecentResponse(remote_device.GetDeviceId(),
+                    prefs::kMostRecentConnectTetheringResponderIds);
 }
 
 std::vector<std::string>
@@ -58,25 +48,10 @@
   return GetDeviceIdsForPref(prefs::kMostRecentConnectTetheringResponderIds);
 }
 
-void TetherHostResponseRecorder::
-    NotifyObserversPreviouslyConnectedHostIdsChanged() {
-  for (Observer& observer : observer_list_) {
-    observer.OnPreviouslyConnectedHostIdsChanged();
-  }
-}
-
-bool TetherHostResponseRecorder::AddRecentResponse(
+void TetherHostResponseRecorder::AddRecentResponse(
     const std::string& device_id,
     const std::string& pref_name) {
   const base::ListValue* ids = pref_service_->GetList(pref_name);
-
-  std::string first_device_id_in_list;
-  ids->GetString(0u, &first_device_id_in_list);
-  if (device_id == first_device_id_in_list) {
-    // If the device ID that is being inserted is already at the front of the
-    // list, there is nothing to do.
-    return false;
-  }
 
   // Create a mutable copy of the stored IDs, or create one if it has yet to be
   // stored.
@@ -93,8 +68,6 @@
 
   // Store the updated list back in |pref_service_|.
   pref_service_->Set(pref_name, *updated_ids);
-
-  return true;
 }
 
 std::vector<std::string> TetherHostResponseRecorder::GetDeviceIdsForPref(