void flushCompositingBits()

Updates the needsCompositing bits.

Called as part of the rendering pipeline after flushLayout and before flushPaint.

Source 

void flushCompositingBits() {
  Timeline.startSync('Compositing bits');
  _nodesNeedingCompositingBitsUpdate.sort((RenderObject a, RenderObject b) => a.depth - b.depth);
  for (RenderObject node in _nodesNeedingCompositingBitsUpdate) {
    if (node._needsCompositingBitsUpdate && node.owner == this)
      node._updateCompositingBits();
  }
  _nodesNeedingCompositingBitsUpdate.clear();
  Timeline.finishSync();
}