Bluetooth: macOS: DidModifyServices can happens while scanning

device/bluetooth/bluetooth_remote_gatt_characteristic_mac.h

 // Copyright 2016 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.
 
 #ifndef DEVICE_BLUETOOTH_BLUETOOTH_REMOTE_GATT_CHARACTERISTIC_MAC_H_
 #define DEVICE_BLUETOOTH_BLUETOOTH_REMOTE_GATT_CHARACTERISTIC_MAC_H_
 
 #include "device/bluetooth/bluetooth_remote_gatt_characteristic.h"
 
 #import <CoreBluetooth/CoreBluetooth.h>
@@ skipping 87 matching lines @@
   bool IsDiscoveryComplete() const;
   // Returns BluetoothRemoteGattDescriptorMac from CBDescriptor.
   BluetoothRemoteGattDescriptorMac* GetBluetoothRemoteGattDescriptorMac(
       CBDescriptor* cb_descriptor) const;
   bool HasPendingRead() const {
     return !read_characteristic_value_callbacks_.first.is_null();
   };
   bool HasPendingWrite() const {
     return !write_characteristic_value_callbacks_.first.is_null();
   };
-  // Is true if the characteristic has been discovered with all its descriptors.
+  // Is true if the characteristic has been discovered with all its descriptors
+  // and discovery_pending_count_ is 0.
   bool is_discovery_complete_;
+  // Increased each time DiscoverDescriptors() is called. And decreased when
+  // DidDiscoverDescriptors() is called.
+  int discovery_pending_count_;
   // gatt_service_ owns instances of this class.
   BluetoothRemoteGattServiceMac* gatt_service_;
   // A characteristic from CBPeripheral.services.characteristics.
   base::scoped_nsobject<CBCharacteristic> cb_characteristic_;
   // Characteristic identifier.
   std::string identifier_;
   // Service UUID.
   BluetoothUUID uuid_;
   // Characteristic value.
   std::vector<uint8_t> value_;
@@ skipping 15 matching lines @@
 };
 
 // Stream operator for logging.
 DEVICE_BLUETOOTH_EXPORT std::ostream& operator<<(
     std::ostream& out,
     const BluetoothRemoteGattCharacteristicMac& characteristic);
 
 }  // namespace device
 
 #endif  // DEVICE_BLUETOOTH_BLUETOOTH_REMOTE_GATT_CHARACTERISTIC_MAC_H_