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.
'componentWillUnmount method.%s',
      ReactCurrentFiber.getStackByFiberInDevAndProd(fiber),
    );
    didWarnStateUpdateForUnmountedComponent[componentName] = true;
  };
  warnAboutInvalidUpdates = function(instance: React$Component<any>) {
    switch (ReactCurrentFiber.phase) {
      case 'getChildContext':
        if (didWarnSetStateChildContext) {
          return;
        }
        warningWithoutStack(
          false,
          'setState(...): Cannot call setState() inside getChildContext()',
        );
        didWarnSetStateChildContext = true;
        break;
      case 'render':
        if (didWarnAboutStateTransition) {
          return;
        }
        warningWithoutStack(
          false,
          'Cannot update during an existing state transition (such as within ' +
            '`render`). Render methods should be a pure function of props and state.',
        );
        didWarnAboutStateTransition = true;
        break;
    }
  };