Probably not. The XaoS algorithm depends on nearest-neighbour scaling and recalculating just the interpolated rows/columns. You could do that in a texture then scale the texture to the screen with WebGL, but it probably wouldn't be any more efficient than just doing it in a non-accellerated frame-buffer.

If there was a way to offload the Mandelbrot calculations to the GPU, that might make things faster, depending on how tedious it would be to composite them back onto the framebuffer afterward.

Here's a Mandelbrot zoomer implemented entirely with WebGL:

http://learningwebgl.com/lessons/example01/

It doesn't use the XaoS algorithm, it recalculates the entire frame from scratch on the GPU. On my machine at least, it's noticeably choppier than the XaoS version, and at a smaller frame-size, too.