There were two problems stopping the KMS winsys from working with a
GLES2 driver:
• When creating the EGL context, it was missing the attribute to
select the client version so it would end up with the GLES1 API.
• When creating the depth buffer for the framebuffer it was using
GL_DEPTH_COMPONENT but only GL_DEPTH_COMPONENT16 is supported on
GLES. cogl-framebuffer already unconditionally uses this so it
probably makes sense to do the same here.
Reviewed-by: Robert Bragg <robert@linux.intel.com>
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