title: Provide tab title with reportlab generated pdf
body: <p>This question is really simple, but I can't find any data on it.
  When I generate a pdf with reportlab, passing the httpresponse as a file, browsers that are configured to show files display the pdf correctly. However, the title of the tab remains "(Anonymous) 127.0.0.1/whatnot", which is kinda ugly for the user.</p>
  
  <p>Since most sites are able to somehow display an appropiate title, I think it's doable... Is there some sort of title parameter that I can pass to the pdf? Or some header for the response? This is my code:</p>
  
  <pre><code>def render_pdf_report(self, context, file_name):
      response = HttpResponse(content_type='application/pdf')
      response['Content-Disposition'] = 'filename="{}"'.format(file_name)
  
      document = BaseDocTemplate(response, **self.get_create_document_kwargs())
      #  pdf generation code
      document.build(story)
      return response
  </code></pre>