Remove the pesto gallery demo (#9341)

examples/flutter_gallery/lib/gallery/item.dart

@@ -49,17 +49,11 @@ class GalleryItem extends StatelessWidget {
   }
 }
 
-// When editing this list, make sure you keep it in sync with
-// the list in ../../test_driver/transitions_perf_test.dart
-final List<GalleryItem> kAllGalleryItems = <GalleryItem>[
+List<GalleryItem> _buildGalleryItems() {
+  // When editing this list, make sure you keep it in sync with
+  // the list in ../../test_driver/transitions_perf_test.dart
+  final List<GalleryItem> galleryItems = <GalleryItem>[
     // Demos
-  new GalleryItem(
-    title: 'Pesto',
-    subtitle: 'Simple recipe browser',
-    category: 'Demos',
-    routeName: PestoDemo.routeName,
-    buildRoute: (BuildContext context) => new PestoDemo(),
-  ),
     new GalleryItem(
       title: 'Shrine',
       subtitle:'Basic shopping app',
@@ -322,4 +316,24 @@ final List<GalleryItem> kAllGalleryItems = <GalleryItem>[
       routeName: TypographyDemo.routeName,
       buildRoute: (BuildContext context) => new TypographyDemo(),
     )
-];
+  ];
+
+  // Keep Pesto around for its regression test value. It is not included
+  // in (release builds) the performance tests.
+  assert(() {
+    galleryItems.insert(0,
+      new GalleryItem(
+        title: 'Pesto',
+        subtitle: 'Simple recipe browser',
+        category: 'Demos',
+        routeName: PestoDemo.routeName,
+        buildRoute: (BuildContext context) => new PestoDemo(),
+      ),
+    );
+    return true;
+  });
+
+  return galleryItems;
+}
+
+final List<GalleryItem> kAllGalleryItems = _buildGalleryItems();

examples/flutter_gallery/test_driver/transitions_perf_test.dart

@@ -33,7 +33,6 @@ class Demo {
 // kAllGalleryItems.map((GalleryItem item) => item.title).toList();
 const List<Demo> demos = const <Demo>[
   // Demos
-  const Demo('Pesto', profiled: true),
   const Demo('Shrine', profiled: true),
   const Demo('Contact profile', profiled: true),
   const Demo('Animation', profiled: true),