Clean up HID backend and API.

device/hid/hid_service_win.cc

 // Copyright (c) 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.
 
 #include "device/hid/hid_service_win.h"
 
 #include <cstdlib>
 #include <string>
 
 #include "base/callback_helpers.h"
@@ skipping 128 matching lines @@
 
     if (!res)
       continue;
 
     PlatformAddDevice(device_interface_detail_data->DevicePath);
   }
 
   return true;
 }
 
-void HidServiceWin::PlatformAddDevice(std::string device_path) {
+void HidServiceWin::PlatformAddDevice(const std::string& device_path) {
   HidDeviceInfo device_info;
   device_info.device_id = device_path;
 
   // Try to open the device.
   base::win::ScopedHandle device_handle(
       CreateFileA(device_path.c_str(),
                   0,
                   FILE_SHARE_READ | FILE_SHARE_WRITE,
                   NULL,
                   OPEN_EXISTING,
@@ skipping 50 matching lines @@
 
   if (HidD_GetProductString(device_handle.Get(),
                             str_property,
                             sizeof(str_property))) {
     device_info.product_name = base::SysWideToUTF8(str_property);
   }
 
   HidService::AddDevice(device_info);
 }
 
-void HidServiceWin::PlatformRemoveDevice(std::string device_path) {
+void HidServiceWin::PlatformRemoveDevice(const std::string& device_path) {
   HidService::RemoveDevice(device_path);
 }
 
 void HidServiceWin::GetDevices(std::vector<HidDeviceInfo>* devices) {
   Enumerate();
   HidService::GetDevices(devices);
 }
 
-scoped_refptr<HidConnection> HidServiceWin::Connect(std::string device_id) {
+scoped_refptr<HidConnection> HidServiceWin::Connect(
+    const std::string& device_id) {
   if (!ContainsKey(devices_, device_id)) return NULL;
   scoped_refptr<HidConnectionWin> connection(
       new HidConnectionWin(devices_[device_id]));
   if (!connection->available()) {
     LOG_GETLASTERROR(ERROR) << "Failed to open device.";
     return NULL;
   }
   return connection;
 }
 
 }  // namespace device