Implement BluetoothRemoteGattCharacteristicWin::StartNotifySession and related unit tests

device/bluetooth/bluetooth_device_win.cc

Index: device/bluetooth/bluetooth_device_win.cc
diff --git a/device/bluetooth/bluetooth_device_win.cc b/device/bluetooth/bluetooth_device_win.cc
index 561b5a7c6532bb92298f355d70b32c07ca0dec53..363da1d1e02f5a9850e66eadbdcf55f189210146 100644
--- a/device/bluetooth/bluetooth_device_win.cc
+++ b/device/bluetooth/bluetooth_device_win.cc
@@ -43,6 +43,15 @@ BluetoothDeviceWin::BluetoothDeviceWin(
 }
 
 BluetoothDeviceWin::~BluetoothDeviceWin() {
+  // Explicitly take and erase GATT services one by one to ensure that calling
+  // GetGattService on removed service in GattServiceRemoved returns null.
+  std::vector<std::string> service_keys;
+  for (const auto& gatt_service : gatt_services_) {
+    service_keys.push_back(gatt_service.first);
+  }
+  for (const auto& key : service_keys) {
+    gatt_services_.take_and_erase(key);
+  }
 }
 
 uint32_t BluetoothDeviceWin::GetBluetoothClass() const {