code: function _showEditor(document, pane, editorOptions) {
          // Ensure a main editor exists for this document to show in the UI
          var createdNewEditor = false,
              editor = document._masterEditor;
  
          // Check if a master editor is not set already or the current master editor doesn't belong
          // to the pane container requested - to support creation of multiple full editors
          // This check is required as _masterEditor is the active full editor for the document
          // and there can be existing full editor created for other panes
          if (editor && editor._paneId && editor._paneId !== pane.id) {
              editor = document._checkAssociatedEditorForPane(pane.id);
          }
  
          if (!editor) {
              // Performance (see #4757) Chrome wastes time messing with selection
              // that will just be changed at end, so clear it for now
              if (window.getSelection && window.getSelection().empty) {  // Chrome
                  window.getSelection().empty();
              }
  
              // Editor doesn't exist: populate a new Editor with the text
              editor = _createFullEditorForDocument(document, pane, editorOptions);
              createdNewEditor = true;
          } else if (editor.$el.parent()[0] !== pane.$content[0]) {
              // editor does exist but is not a child of the pane so add it to the
              //  pane (which will switch the view's container as well)
              pane.addView(editor);
          }
  
          // show the view
          pane.showView(editor);
  
          if (MainViewManager.getActivePaneId() === pane.id) {
              // give it focus
              editor.focus();
          }
  
          if (createdNewEditor) {
              _restoreEditorViewState(editor);
          }
      }
docs: Create and/or show the editor for the specified document
  @param {!Document} document - document to edit
  @param {!Pane} pane - pane to show it in
  @param {!Object} editorOptions - If specified, contains
  editor options that can be passed to CodeMirror
  @private