Create a FakeTetherService, which stubs out TetherService for development.

chrome/browser/chromeos/tether/tether_service.cc

 // 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.
 
 #include "chrome/browser/chromeos/tether/tether_service.h"
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/macros.h"
 #include "base/memory/ptr_util.h"
@@ skipping 158 matching lines @@
     profile_->GetPrefs()->SetBoolean(prefs::kInstantTetheringEnabled,
                                      is_enabled);
     UpdateTetherTechnologyState();
   }
 }
 
 void TetherService::OnPrefsChanged() {
   UpdateTetherTechnologyState();
 }
 
+bool TetherService::HasSyncedTetherHosts() const {
+  return !cryptauth_service_->GetCryptAuthDeviceManager()
+              ->GetTetherHosts()
+              .empty();
+}
+
 void TetherService::UpdateTetherTechnologyState() {
   chromeos::NetworkStateHandler::TechnologyState tether_technology_state =
       GetTetherTechnologyState();
 
   network_state_handler_->SetTetherTechnologyState(tether_technology_state);
 
   if (tether_technology_state ==
       chromeos::NetworkStateHandler::TechnologyState::TECHNOLOGY_ENABLED) {
     StartTetherIfEnabled();
   } else {
@@ skipping 24 matching lines @@
   return chromeos::NetworkStateHandler::TechnologyState::TECHNOLOGY_ENABLED;
 }
 
 void TetherService::OnBluetoothAdapterFetched(
     scoped_refptr<device::BluetoothAdapter> adapter) {
   adapter_ = adapter;
   adapter_->AddObserver(this);
   UpdateTetherTechnologyState();
 }
 
-bool TetherService::HasSyncedTetherHosts() const {
-  return !cryptauth_service_->GetCryptAuthDeviceManager()
-              ->GetTetherHosts()
-              .empty();
-}
-
 bool TetherService::IsFeatureFlagEnabled() const {
   return base::CommandLine::ForCurrentProcess()->HasSwitch(
       chromeos::switches::kEnableTether);
 }
 
 bool TetherService::IsBluetoothAvailable() const {
   return adapter_.get() && adapter_->IsPresent() && adapter_->IsPowered();
 }
 
 bool TetherService::IsAllowedByPolicy() const {
   return profile_->GetPrefs()->GetBoolean(prefs::kInstantTetheringAllowed);
 }
 
 bool TetherService::IsEnabledbyPreference() const {
   return profile_->GetPrefs()->GetBoolean(prefs::kInstantTetheringEnabled);
 }