gl: optimize resolve and blitting in glesv3

When resolve a surface, we set content_in_texture = TRUE to avoid
repeating of resolving.  When blitting back to renderbuffer, we
check if the content_changed, if no content change, we don't blit
gl/msaa: compute bounds for paint and mask

Compute bounds for paint and mask can reduce number of pixel to be filled
in CAIRO_OVER_OPERATOR
wip