cros: Init SystemTrayDelegate earlier to break bluetooth init dependency

chrome/browser/ui/ash/tray_bluetooth_helper_unittest.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/ui/ash/tray_bluetooth_helper.h"
 
 #include <vector>
 
 #include "ash/common/system/tray/system_tray_delegate.h"
 #include "ash/test/ash_test_base.h"
 #include "device/bluetooth/dbus/bluez_dbus_manager.h"
 #include "device/bluetooth/dbus/fake_bluetooth_adapter_client.h"
 
 using bluez::BluezDBusManager;
 using bluez::FakeBluetoothAdapterClient;
 
 using TrayBluetoothHelperTest = ash::test::AshTestBase;
 
 // Tests basic functionality like turning Bluetooth on and off.
 TEST_F(TrayBluetoothHelperTest, Basics) {
   // Set Bluetooth discovery simulation delay to 0 so the test doesn't have to
   // wait or use timers.
   FakeBluetoothAdapterClient* adapter_client =
       static_cast<FakeBluetoothAdapterClient*>(
           BluezDBusManager::Get()->GetBluetoothAdapterClient());
   adapter_client->SetSimulationIntervalMs(0);
 
-  TrayBluetoothHelper helper(nullptr);
+  TrayBluetoothHelper helper;
   helper.Initialize();
   RunAllPendingInMessageLoop();
   EXPECT_TRUE(helper.GetAvailable());
   EXPECT_FALSE(helper.GetEnabled());
   EXPECT_FALSE(helper.HasDiscoverySession());
   EXPECT_FALSE(helper.IsDiscovering());
 
   std::vector<ash::BluetoothDeviceInfo> devices;
   helper.GetAvailableDevices(&devices);
   // The devices are fake in tests, so don't assume any particular number.
@@ skipping 12 matching lines @@
   helper.StopDiscovering();
   RunAllPendingInMessageLoop();
   EXPECT_FALSE(helper.HasDiscoverySession());
   EXPECT_FALSE(helper.IsDiscovering());
 
   // Turn Bluetooth off.
   helper.ToggleEnabled();
   RunAllPendingInMessageLoop();
   EXPECT_FALSE(helper.GetEnabled());
 }