docs: public void onProximityChange(final boolean onProximity) {
          new ExecutionChain(mGvrContext).runOnMainThread(new Runnable() {
              @Override
              public void run() {
                  if (!mContentSceneViewStack.isEmpty()) {
                      mContentSceneViewStack.peek().onProximityChange(onProximity);
                  }
              }
          }).execute();
      }