McDonald’s Corp. Chief Executive Officer Steve Easterbrook promised to give details of his turnaround plan for the struggling chain next month, following another quarter of declining sales and profit. “We are developing a turnaround plan to improve our performance and deliver enduring profitable growth,” Easterbrook said in a statement Wednesday. The prospect of a comeback plan placated investors after McDonald’s profit missed analysts’ estimates and the company posted a sixth straight quarter of decreasing U.S. sales.