Nest some more namespaces

Did someone previously suggest that all namespace had been
nested?  Silly.

Signed-off-by: Stephan Pleines <pleines.stephan@gmail.com>
Change-Id: I22278c1caaeba8b47dc46fb2ed3078c20a11e190
diff --git a/aos/vision/debug/debug_window.h b/aos/vision/debug/debug_window.h
index 573cef5..dcbc5f7 100644
--- a/aos/vision/debug/debug_window.h
+++ b/aos/vision/debug/debug_window.h
@@ -8,8 +8,7 @@
 #include "aos/vision/debug/overlay.h"
 #include "aos/vision/image/image_types.h"
 
-namespace aos {
-namespace vision {
+namespace aos::vision {
 
 // Implement Cairo version of RenderInterface.
 class CairoRender : public RenderInterface {
@@ -84,7 +83,6 @@
   std::unique_ptr<Internals> self;
 };
 
-}  // namespace vision
-}  // namespace aos
+}  // namespace aos::vision
 
 #endif  // AOS_VISION_DEBUG_DEBUG_WINDOW_H_