#!/bin/sh chromium <path> & matchbox-window-manager -use_titlebar no
Please note, that behind the line including matxhbox don't add an &. The xserver ends, if the script .xsession ends.
With an ending ampersand &, the .xsession script moves all programs into the background and stops. This leads to a crazy behaviour of the xserver. The xserver starts and runs .xsession and stops. This procedure starts after some seconds again and so on.
Don't forget to install xorg package. On minimal system you should add alsa-base package and alsa-utils package for sound.