cros: Init SystemTrayDelegate earlier to break bluetooth init dependency

chrome/browser/ui/ash/tray_bluetooth_helper.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 CHROME_BROWSER_UI_ASH_TRAY_BLUETOOTH_HELPER_H_
 #define CHROME_BROWSER_UI_ASH_TRAY_BLUETOOTH_HELPER_H_
 
 #include <memory>
 #include <vector>
 
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
 #include "device/bluetooth/bluetooth_adapter.h"
 
 namespace ash {
 struct BluetoothDeviceInfo;
 }
 
-namespace chromeos {
-class SystemTrayDelegateChromeOS;
-}
-
 namespace device {
 class BluetoothDiscoverySession;
 }
 
 // Maps UI concepts from the Bluetooth system tray (e.g. "Bluetooth is on") into
 // device concepts ("Bluetooth adapter enabled"). Note that most Bluetooth
 // device operations are asynchronous, hence the two step initialization.
 // TODO(jamescook): Move into //ash/system next to TrayBluetooth. This isn't
 // named "delegate" because long-term there should not be any delegation.
 class TrayBluetoothHelper : public device::BluetoothAdapter::Observer {
  public:
-  explicit TrayBluetoothHelper(
-      chromeos::SystemTrayDelegateChromeOS* system_tray_delegate);
+  TrayBluetoothHelper();
   ~TrayBluetoothHelper() override;
 
   // Called after SystemTray has been instantiated.
   void Initialize();
 
   // Completes initialization after the Bluetooth adapter is ready.
   void InitializeOnAdapterReady(
       scoped_refptr<device::BluetoothAdapter> adapter);
 
   // Returns a list of available bluetooth devices.
@@ skipping 37 matching lines @@
                    device::BluetoothDevice* device) override;
   void DeviceChanged(device::BluetoothAdapter* adapter,
                      device::BluetoothDevice* device) override;
   void DeviceRemoved(device::BluetoothAdapter* adapter,
                      device::BluetoothDevice* device) override;
 
  private:
   void OnStartDiscoverySession(
       std::unique_ptr<device::BluetoothDiscoverySession> discovery_session);
 
-  // TODO: Eliminate this after verifying the initialization order of
-  // SystemTrayDelegateChromeOS can be changed.
-  chromeos::SystemTrayDelegateChromeOS* const system_tray_delegate_;
-
   bool should_run_discovery_ = false;
   scoped_refptr<device::BluetoothAdapter> adapter_;
   std::unique_ptr<device::BluetoothDiscoverySession> discovery_session_;
 
   // Object could be deleted during a prolonged Bluetooth operation.
   base::WeakPtrFactory<TrayBluetoothHelper> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(TrayBluetoothHelper);
 };
 
 #endif  // CHROME_BROWSER_UI_ASH_TRAY_BLUETOOTH_HELPER_H_