code: function _pauseAssetGeneration(id) {
          if (_waitingDocuments.hasOwnProperty(id)) {
              _canceledDocuments[id] = true;
          } else if (_assetManagers.hasOwnProperty(id)) {
              _assetManagers[id].stop();
          }
      }
docs: Disable asset generation for the given Document ID, halting any asset
  rending in progress.
  
  @private
  @param {!number} id The document ID for which asset generation should be disabled.