Bluetooth: macOS: DidModifyServices can happens while scanning

device/bluetooth/test/mock_bluetooth_cbperipheral_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/test/mock_bluetooth_cbperipheral_mac.h"
 
 #include "base/mac/foundation_util.h"
 #include "base/mac/scoped_nsobject.h"
 #include "device/bluetooth/test/bluetooth_test_mac.h"
 #include "device/bluetooth/test/mock_bluetooth_cbcharacteristic_mac.h"
@@ skipping 75 matching lines @@
 }
 
 - (void)discoverCharacteristics:(NSArray*)characteristics
                      forService:(CBService*)service {
   if (_bluetoothTestMac) {
     _bluetoothTestMac->OnFakeBluetoothCharacteristicDiscovery();
   }
 }
 
 - (void)discoverDescriptorsForCharacteristic:(CBCharacteristic*)characteristic {
-  MockCBCharacteristic* mock_characteristic =
-      ObjCCast<MockCBCharacteristic>(characteristic);
-  [mock_characteristic discoverDescriptors];
 }
 
 - (void)readValueForCharacteristic:(CBCharacteristic*)characteristic {
   DCHECK(_bluetoothTestMac);
   _bluetoothTestMac->OnFakeBluetoothCharacteristicReadValue();
 }
 
 - (void)writeValue:(NSData*)data
     forCharacteristic:(CBCharacteristic*)characteristic
                  type:(CBCharacteristicWriteType)type {
@@ skipping 29 matching lines @@
                                                    base::scoped_policy::RETAIN);
   DCHECK(serviceToRemove);
   [_services.get() removeObject:serviceToRemove];
   [self didModifyServices:@[ serviceToRemove ]];
 }
 
 - (void)mockDidDiscoverServices {
   [_delegate peripheral:self.peripheral didDiscoverServices:nil];
 }
 
+- (void)mockDidDiscoverCharacteristicsForService:(CBService*)service {
+  [_delegate peripheral:self.peripheral
+      didDiscoverCharacteristicsForService:service
+                                     error:nil];
+}
+
+- (void)mockDidDiscoverDescriptorsForCharacteristic:
+    (CBCharacteristic*)characteristic {
+  [_delegate peripheral:self.peripheral
+      didDiscoverDescriptorsForCharacteristic:characteristic
+                                        error:nil];
+}
+
 - (void)mockDidDiscoverEvents {
   [self mockDidDiscoverServices];
   // BluetoothLowEnergyDeviceMac is expected to call
   // -[CBPeripheral discoverCharacteristics:forService:] for each services,
   // so -[<CBPeripheralDelegate peripheral:didDiscoverCharacteristicsForService:
   // error:] needs to be called for all services.
   for (CBService* service in _services.get()) {
-    [_delegate peripheral:self.peripheral
-        didDiscoverCharacteristicsForService:service
-                                       error:nil];
+    [self mockDidDiscoverCharacteristicsForService:service];
     for (CBCharacteristic* characteristic in service.characteristics) {
       // After discovering services, BluetoothLowEnergyDeviceMac is expected to
       // discover characteristics for all services.
       [_delegate peripheral:self.peripheral
           didDiscoverDescriptorsForCharacteristic:characteristic
                                             error:nil];
     }
   }
 }
 
@@ skipping 26 matching lines @@
   return ObjCCast<CBPeripheral>(self);
 }
 
 - (void)setNotifyValue:(BOOL)notification
      forCharacteristic:(CBCharacteristic*)characteristic {
   _bluetoothTestMac->OnFakeBluetoothGattSetCharacteristicNotification(
       notification == YES);
 }
 
 @end