Add errors for various chooser failure modes, and remove assertions that are about to change.

public/platform/modules/bluetooth/WebBluetoothError.h

 // Copyright 2014 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 WebBluetoothError_h
 #define WebBluetoothError_h
 
 namespace blink {
 
 // Errors that can occur during Web Bluetooth execution, which are transformed
@@ skipping 18 matching lines @@
     ConnectUnknownFailure,
     ConnectAuthFailed,
     ConnectAuthCanceled,
     ConnectAuthRejected,
     ConnectAuthTimeout,
     ConnectUnsupportedDevice,
     UntranslatedConnectErrorCode,
     // NotFoundError:
     BluetoothAdapterOff,
     NoBluetoothAdapter,
+    NoBluetoothChooser,
     DiscoverySessionStartFailed,
     DiscoverySessionStopFailed,
     NoDevicesFound,
+    ChosenDeviceVanished,
+    ChooserCancelled,
     ServiceNotFound,
     CharacteristicNotFound,
     // NotSupportedError:
     GATTUnknownError,
     GATTUnknownFailure,
     GATTNotPermitted,
     GATTNotSupported,
     GATTUntranslatedErrorCode,
     // SecurityError:
     GATTNotAuthorized,
     RequestDeviceWithoutFrame,
     // SyntaxError:
 
     ENUM_MAX_VALUE = GATTNotAuthorized,
 };
 
 } // namespace blink
 
 #endif // WebBluetoothError_h