docs: function unsubscribe(handler) {
          for (var i = handlers.length - 1; i >= 0; --i) {
              if (handlers[i] === handler) {
                  handlers.splice(i, 1);
              }
          }
  
          if (handlers.length === 0) {
              window.onerror = _oldOnerrorHandler;
              _onErrorHandlerInstalled = false;
          }
      }