code: function _destroyEditorIfNotNeeded(document) {
          if (!(document instanceof DocumentManager.Document)) {
              throw new Error("_destroyEditorIfUnneeded() should be passed a Document");
          }
          if (document._masterEditor) {
              // findPaneForDocument tries to locate the pane in which the document
              //  is either opened or will be opened (in the event that the document is
              //  in a working set but has yet to be opened) and then asks the pane
              //  to destroy the view if it doesn't need it anymore
              var pane = _findPaneForDocument(document);
  
              if (pane) {
                  // let the pane deceide if it wants to destroy the view if it's no needed
                  pane.destroyViewIfNotNeeded(document._masterEditor);
              } else {
                  // in this case, the document isn't referenced at all so just destroy it
                  document._masterEditor.destroy();
              }
          }
      }
docs: Destroys an editor object if a document is no longer referenced
  @param {!Document} doc - document to destroy