src/vs/editor/contrib/gotoSymbol/browser/symbolNavigation.ts/EditorState/constructor
class EditorState:	constructor(@ICodeEditorService editorService: ICodeEditorService) {
		this._disposables.add(editorService.onCodeEditorRemove(this._onDidRemoveEditor, this));
		this._disposables.add(editorService.onCodeEditorAdd(this._onDidAddEditor, this));
		editorService.listCodeEditors().forEach(this._onDidAddEditor, this);
	}