pub fn create_new_external_array_buffer<T>(
    cx: JSContext,
    mapping: Arc<Mutex<Vec<T::Element>>>,
    offset: usize,
    range_size: usize,
    m_end: usize
) -> HeapBufferSource<T>where
    T: TypedArrayElement + TypedArrayElementCreator,
    T::Element: Clone + Copy,