Drop redundant DecodeImageCallbacks subclass
diff --git a/example/imageviewer/imageviewer.cc b/example/imageviewer/imageviewer.cc
index c196ee7..3b12f89 100644
--- a/example/imageviewer/imageviewer.cc
+++ b/example/imageviewer/imageviewer.cc
@@ -89,17 +89,6 @@
 wuffs_base__slice_u8 g_pixbuf_mem_slice = {0};
 uint32_t g_background_color_index = 0;
 
-class MyCallbacks : public wuffs_aux::DecodeImageCallbacks {
- public:
-  // This override is redundant - it is the same as the default
-  // implementation. It exists because this is example code and shows how to
-  // decode to other pixel formats such as BGR_565 or RGBA_NONPREMUL.
-  wuffs_base__pixel_format  //
-  SelectPixfmt(const wuffs_base__image_config& image_config) override {
-    return wuffs_base__make_pixel_format(WUFFS_BASE__PIXEL_FORMAT__BGRA_PREMUL);
-  }
-};
-
 bool  //
 load_image(const char* filename) {
   FILE* file = stdin;
@@ -119,7 +108,7 @@
   g_pixbuf_mem_owner.reset();
   g_pixbuf_mem_slice = wuffs_base__empty_slice_u8();
 
-  MyCallbacks callbacks;
+  wuffs_aux::DecodeImageCallbacks callbacks;
   wuffs_aux::sync_io::FileInput input(file);
   wuffs_aux::DecodeImageResult res = wuffs_aux::DecodeImage(
       callbacks, input,