code: public void writingState()
      {
          if (!this.writtenState)
          {
              this.writtenState = true;
              this.writtenStateWithoutWrapper = false;
              this.fast = new FastWriter(this.initialSize);
              this.out = this.fast;
          }
      }
docs: Mark that state is about to be written. Contrary to what you'd expect, we cannot and should not assume that this
  location is really going to have state; it is perfectly legit to have a ResponseWriter that filters out content,
  and ignores an attempt to write out state at this point. So, we have to check after the fact to see if there
  really are state markers.