The CSS files in the BokehJS directory.

def css_files(self):
        ''' The CSS files in the BokehJS directory.

        '''
        bokehjsdir = self.bokehjsdir()
        js_files = []
        for root, dirnames, files in os.walk(bokehjsdir):
            for fname in files:
                if fname.endswith(".css"):
                    js_files.append(join(root, fname))
        return js_files