Finish https://codereview.chromium.org/1948763003

device/bluetooth/bluetooth_low_energy_device_mac.mm

 // 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 "device/bluetooth/bluetooth_low_energy_device_mac.h"
 
 #import <CoreFoundation/CoreFoundation.h>
 #include <stddef.h>
 
 #include "base/mac/mac_util.h"
@@ skipping 234 matching lines @@
             << error.localizedDescription.UTF8String << " (" << error.domain
             << ": " << error.code << ")";
     return;
   }
   for (CBService* cb_service in GetPeripheral().services) {
     BluetoothRemoteGattServiceMac* gatt_service =
         GetBluetoothRemoteGattService(cb_service);
     if (!gatt_service) {
       gatt_service = new BluetoothRemoteGattServiceMac(this, cb_service,
                                                        true /* is_primary */);
-      gatt_services_.add(gatt_service->GetIdentifier(),
-                         base::WrapUnique(gatt_service));
+      auto result_iter = gatt_services_.add(gatt_service->GetIdentifier(),
+                                            base::WrapUnique(gatt_service));
+      DCHECK(result_iter.second);
       adapter_->NotifyGattServiceAdded(gatt_service);
     }
   }
   // TODO(http://crbug.com/609064): Services are fully discovered once all
   // characteristics have been found.
   SetGattServicesDiscoveryComplete(true);
   adapter_->NotifyGattServicesDiscovered(this);
 }
 
 void BluetoothLowEnergyDeviceMac::DidModifyServices(
@@ skipping 64 matching lines @@
   for (const auto& key : service_keys) {
     gatt_services_.take_and_erase(key);
   }
   if (create_gatt_connection_error_callbacks_.empty()) {
     // TODO(http://crbug.com/585897): Need to pass the error.
     DidDisconnectGatt();
   } else {
     DidFailToConnectGatt(error_code);
   }
 }