def GenerateImageSet(images, quote):
  """Generates a -webkit-image-set for the provided list of images.

  Args:
    images: an array of tuples giving scale factor and file path
            (i.e. [('1x', 'image.png'), ('2x', '2x/image.png')]).
    quote: a string giving the quotation character to use (i.e. "'")

  Returns:
    string giving a -webkit-image-set rule referencing the provided images.
        (i.e. '-webkit-image-set(url('image.png') 1x, url('2x/image.png') 2x)')
  """
  imageset = []
  for (scale_factor, filename) in images:
    imageset.append("url(%s%s%s) %s" % (quote, filename, quote, scale_factor))
  return "-webkit-image-set(%s)" % (', '.join(imageset))