src/vs/workbench/contrib/preferences/browser/preferences.contribution.ts/DefaultPreferencesEditorInputSerializer/serialize
class DefaultPreferencesEditorInputSerializer:	serialize(editorInput: EditorInput): string {
		const input = <DefaultPreferencesEditorInput>editorInput;

		const serialized: ISerializedDefaultPreferencesEditorInput = { resource: input.resource.toString() };

		return JSON.stringify(serialized);
	}