Currently, we estimate the expected render time purely based on the
latency policy.

The problem with doing so is that the real render time might be larger,
this can result in frame drops.

In order to avoid frame drops, we need to take into account previous
render times while estimating the next render time. For now, we just
measure how long it takes to record rendering commands on the CPU.

In the future, we might want consider using OpenGL timer queries for
measuring the real render time, but for now, it's good enough.