Cleanup: Pass std::string as const reference if possible

components/proximity_auth/ble/bluetooth_low_energy_connection_finder.cc

 // Copyright 2015 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 "components/proximity_auth/ble/bluetooth_low_energy_connection_finder.h"
 
 #include <string>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
@@ skipping 296 matching lines @@
     StartDiscoverySession();
   } else {
     base::ThreadTaskRunnerHandle::Get()->PostTask(
         FROM_HERE, base::Bind(&BluetoothLowEnergyConnectionFinder::
                                   RestartDiscoverySessionWhenReady,
                               weak_ptr_factory_.GetWeakPtr()));
   }
 }
 
 BluetoothDevice* BluetoothLowEnergyConnectionFinder::GetDevice(
-    std::string device_address) {
+    const std::string& device_address) {
   // It's not possible to simply use
   // |adapter_->GetDevice(GetRemoteDeviceAddress())| to find the device with MAC
   // address |GetRemoteDeviceAddress()|. For paired devices,
   // BluetoothAdapter::GetDevice(XXX) searches for the temporary MAC address
   // XXX, whereas |remote_device_.bluetooth_address| is the real MAC address.
   // This is a bug in the way device::BluetoothAdapter is storing the devices
   // (see crbug.com/497841).
   std::vector<BluetoothDevice*> devices = adapter_->GetDevices();
   for (const auto& device : devices) {
     if (device->GetAddress() == device_address)
       return device;
   }
   return nullptr;
 }
 
 void BluetoothLowEnergyConnectionFinder::InvokeCallbackAsync() {
   connection_callback_.Run(connection_.Pass());
 }
 
 }  // namespace proximity_auth