[]webgl遮罩的BUG

设置遮罩想实现转圈进度条的效果
 

                this.mMask.graphics.clear();
                Laya.timer.loop(10,this,this.showMask);

        public showMask():void
        {
            this.mMask.graphics.clear();
           this.mMask.graphics.drawPie(75, 75, 150,-90,-90 + this.ang, "#ffff00");
            this.mMask.parentRepaint();
            //this.mTest.repaint();
            this.ang = this.ang + 1;
            if(this.ang >= 360)
            {
                this.ang = 0;
                //this.mMask.graphics.clear();
            }
        }
定时器设置10，没明显问题，改成200，，，出现严重的闪屏。并且能看到黄色的圆被画出来。
去掉webgl模式正常。