Cleanup: Pass std::string as const reference from ash/ + minor coding style changes in base/

ash/system/bluetooth/tray_bluetooth.cc

 // Copyright (c) 2012 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 "ash/system/bluetooth/tray_bluetooth.h"
 
 #include "ash/session/session_state_delegate.h"
 #include "ash/shell.h"
 #include "ash/system/tray/fixed_sized_scroll_view.h"
 #include "ash/system/tray/hover_highlight_view.h"
@@ skipping 320 matching lines @@
         if (display_name)
           *display_name = device_list[i].display_name;
         return true;
       }
     }
     return false;
   }
 
   // Updates UI of the clicked bluetooth device to show it is being connected
   // or disconnected if such an operation is going to be performed underway.
-  void UpdateClickedDevice(std::string device_id, views::View* item_container) {
+  void UpdateClickedDevice(const std::string& device_id,
+                           views::View* item_container) {
     base::string16 display_name;
     if (FoundDevice(device_id, paired_not_connected_devices_,
                            &display_name)) {
       display_name = l10n_util::GetStringFUTF16(
           IDS_ASH_STATUS_TRAY_BLUETOOTH_CONNECTING, display_name);
 
       item_container->RemoveAllChildViews(true);
       static_cast<HoverHighlightView*>(item_container)
           ->AddCheckableLabel(display_name, true /* highlight */, false);
       scroll_content()->SizeToPreferredSize();
@@ skipping 15 matching lines @@
           ash::UMA_STATUS_AREA_BLUETOOTH_DISABLED :
           ash::UMA_STATUS_AREA_BLUETOOTH_ENABLED);
       delegate->ToggleBluetooth();
     } else {
       if (!delegate->GetBluetoothEnabled())
         return;
       std::map<views::View*, std::string>::iterator find;
       find = device_map_.find(sender);
       if (find == device_map_.end())
         return;
-      std::string device_id = find->second;
+      const std::string device_id = find->second;
       if (FoundDevice(device_id, connecting_devices_, NULL))
         return;
       UpdateClickedDevice(device_id, sender);
       delegate->ConnectToBluetoothDevice(device_id);
     }
   }
 
   // Overridden from ButtonListener.
   void ButtonPressed(views::Button* sender, const ui::Event& event) override {
     ash::SystemTrayDelegate* delegate =
@@ skipping 75 matching lines @@
     detailed_->Update();
 }
 
 void TrayBluetooth::OnBluetoothDiscoveringChanged() {
   if (!detailed_)
     return;
   detailed_->Update();
 }
 
 }  // namespace ash