use canonical module subfolder tree

src/browser/header/tray/mod.rs

@@ -0,0 +1,18 @@
+mod menu;
+mod tab;
+
+use gtk::prelude::BoxExt;
+use gtk::Box;
+
+pub fn new() -> Box {
+    let tray = Box::builder()
+        .orientation(gtk::Orientation::Horizontal)
+        .spacing(8)
+        .build();
+
+    // Compose childs
+    tray.append(&menu::new());
+    tray.append(&tab::new());
+
+    tray
+}