While working on the DevTools profiler, I've noticed that durations are sometimes incorrect. This seems to be vaguely related to high/low priority state updates. Need to track this down more so I'm filing an issue for myself.
fn: (A, B, C0, D) => R,
  a: A,
  b: B,
  c: C0,
  d: D,
): R {
  const previousExpirationContext = expirationContext;
  expirationContext = Sync;
  try {
    return fn(a, b, c, d);
  } finally {
    expirationContext = previousExpirationContext;
  }
}
let firstScheduledRoot: FiberRoot | null = null;
let lastScheduledRoot: FiberRoot | null = null;
let callbackExpirationTime: ExpirationTime = NoWork;