Fix HidService lifetime issues

device/core/device_client.h

 // Copyright 2014 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 DEVICE_CORE_DEVICE_CLIENT_H_
 #define DEVICE_CORE_DEVICE_CLIENT_H_
 
 #include "base/macros.h"
 
 namespace device {
 
+class HidService;
 class UsbService;
 
 // Interface used by consumers of //device APIs to get pointers to the service
 // singletons appropriate for a given embedding application. For an example see
 // //chrome/browser/chrome_device_client.h.
 class DeviceClient {
  public:
   // Construction sets the single instance.
   DeviceClient();
 
   // Destruction clears the single instance.
   ~DeviceClient();
 
   // Returns the single instance of |this|.
   static DeviceClient* Get();
 
   // Returns the UsbService instance for this embedder.
   virtual UsbService* GetUsbService();
 
+  // Returns the HidService instance for this embedder.
+  virtual HidService* GetHidService();
+
  private:
   DISALLOW_COPY_AND_ASSIGN(DeviceClient);
 };
 
 }  // namespace device
 
 #endif  // DEVICE_CORE_DEVICE_CLIENT_H_