public void clear() {
    for (SimpleDiffChangeUi changeUi : myPresentations) {
      if (changeUi != null) changeUi.destroyHighlighter();
    }
    myValidChanges.clear();
    myAllChanges.clear();
    myPresentations.clear();
    myIsContentsEqual = ThreeState.UNSURE;
  }
public void clear()