src/vs/editor/browser/widget/codeEditorWidget.ts/CodeEditorWidget/changeDecorations
class CodeEditorWidget:	public changeDecorations(callback: (changeAccessor: IModelDecorationsChangeAccessor) => any): any {
		if (!this._modelData) {
			// callback will not be called
			return null;
		}
		return this._modelData.model.changeDecorations(callback, this._id);
	}