Is Mesa EGL triple buffered by default?

Hi all,

I have 2 main questions, context to follow:

1. Is Mesa EGL triple buffered by default?
2. If so, is there a setting that might make it strictly double buffered?

## Context
- I am writing a Wayland/OpenGL/EGL application
- Immediately after calling eglSwapBuffers I am querying the buffer age
- Buffer age is consistently `3`
- the EGL surface type has the window bit set and renderable type has
the opengl bit set
- I have used tracing tools (ApiTrace) to the best of my knowhow and I
don't see where I might be generating another frame.

3. If the answers to 1 and 2 above are no, is there something I've
missed or a better tool I could use to debug?

Thanks,
Charlie