make bounds roundOut in raster_cache.

Runtime/flow/raster_cache.cs

         public readonly float devicePixelRatio;
 
         public void draw(Canvas canvas) {
-            var bounds = canvas.getTotalMatrix().mapRect(this.logicalRect).roundOut();
+            var bounds = canvas.getTotalMatrix().mapRect(this.logicalRect).roundOut(this.devicePixelRatio);
 
             D.assert(() => {
                 var textureWidth = Mathf.CeilToInt(bounds.width * this.devicePixelRatio);
                 D.assert(this.image.height == textureHeight);
                 return true;
             });
-
 
             canvas.save();
             try {
 
         RasterCacheResult _rasterizePicture(Picture picture, Matrix3 transform, float devicePixelRatio,
             MeshPool meshPool) {
-            var bounds = transform.mapRect(picture.paintBounds).roundOut();
+            var bounds = transform.mapRect(picture.paintBounds).roundOut(devicePixelRatio);
 
             var desc = new RenderTextureDescriptor(
                 Mathf.CeilToInt((bounds.width * devicePixelRatio)),

Runtime/ui/geometry.cs

                 Mathf.Ceil(this.right), Mathf.Ceil(this.bottom));
         }
 
+        public Rect roundOut(float devicePixelRatio) {
+            return fromLTRB(
+                Mathf.Floor(this.left * devicePixelRatio) / devicePixelRatio, 
+                Mathf.Floor(this.top * devicePixelRatio) / devicePixelRatio,
+                Mathf.Ceil(this.right * devicePixelRatio) / devicePixelRatio, 
+                Mathf.Ceil(this.bottom * devicePixelRatio) / devicePixelRatio);
+        }
+
         public Rect roundIn() {
             return fromLTRB(
                 Mathf.Ceil(this.left), Mathf.Ceil(this.top),