added preload estimate quote usage

pkg/fs/preload.go

@@ -33,7 +33,16 @@ func (q *queue) Add(ph *PreloadHandler, name string, prio int) {
 			return
 		}
 	}
-	*q = append(*q, &Preload{Name: name, ph: ph})
+	p := &Preload{Name: name, ph: ph}
+	*q = append(*q, p)
+	file, err := ph.fs.Open(name)
+	if err == nil {
+		defer file.Close()
+		f, ok := file.(*File)
+		if ok {
+			p.Size = f.size()
+		}
+	}
 	q.Sort()
 }