code: public void pause() {
          new ExecutionChain(mGvrContext).runOnMainThread(new Runnable() {
              @Override
              public void run() {
                  if (!mContentSceneViewStack.isEmpty()) {
                      mContentSceneViewStack.peek().hide();
                      WidgetLib.getTouchManager().setFlingHandler(null);
                  }
              }
          }).execute();
      }
docs: Called on system pause.  The current active content scene moves to invisible state -- see
  {@link ContentScene#hide()}