code: function _edit(paneId, doc, optionsIn) {
          var options = optionsIn || {};
  
          var pane = _getPane(paneId);
  
          // If file is untitled or otherwise not within project tree, add it to
          // working set right now (don't wait for it to become dirty)
          if (doc.isUntitled() || !ProjectManager.isWithinProject(doc.file.fullPath)) {
              addToWorkingSet(paneId, doc.file);
          }
  
          // open document will show the editor if there is one already
          EditorManager.openDocument(doc, pane, options);
          _makeFileMostRecent(paneId, doc.file);
  
          if (!options.noPaneActivate) {
              setActivePaneId(paneId);
          }
      }
docs: Edits a document in the specified pane.
  This function is only used by:
  - Unit Tests (which construct Mock Document objects),
  - by File > New  because there is yet to be an established File object
  - by Find In Files which needs to open documents synchronously in some cases
  Do not use this API it is for internal use only
  @param {!string} paneId - id of the pane in which to open the document
  @param {!Document} doc - document to edit
  @param {{noPaneActivate:boolean=}=} optionsIn - options
  @private