此问题只出现在ios上，game.json开启iOSHighPerformance，iOSHighPerformance+之后，android和pc都是正常的。

然后游戏里执行以下代码，会输出:errMsg:"canvasToTempFilePath:fail"

const w = 750;
const h = 586;
const tmpCanvas = wx.createCanvas();
tmpCanvas.width = w;
tmpCanvas.height = h;
// todo draw something
tmpCanvas.toTempFilePath({
	x: 0,
	y: 0,
	width: w,
	height: h,
	destWidth: w,
	destHeight: h,
	success: (res) => {
		console.log(res);
		resolve(res.tempFilePath);
	},
	fail: (res) => {
		console.warn(res);
		resolve("");
	}
})