Currently, only a subset of GATT errors are fully supported because

For example, there is no way to express INVALID_HANDLE from a BluetoothRemoteGattDescriptor.  This is an error that should result in an InvalidStateError at the javascript level, but currently no GATT error results in this javascript error.

We probably need to enumerate all standard GATT errors in device/bluetooth/bluetooth_gatt_service.h and fix all the code that depends on this.