Simplify macrobencharks/picture_cache (#62219)

dev/benchmarks/macrobenchmarks/lib/src/picture_cache.dart

@@ -10,65 +10,35 @@ class PictureCachePage extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    return Scaffold(
-      body: DefaultTabController(
+    return DefaultTabController(
       length: kTabNames.length, // This is the number of tabs.
-        child: NestedScrollView(
-          key: const Key('nested-scroll'), // this key is used by the driver test
-          headerSliverBuilder: (BuildContext context, bool innerBoxIsScrolled) {
-            // These are the slivers that show up in the "outer" scroll view.
-            return <Widget>[
-              SliverOverlapAbsorber(
-                handle: NestedScrollView.sliverOverlapAbsorberHandleFor(context),
-                sliver: SliverAppBar(
+      child: Scaffold(
+        appBar: AppBar(
           title: const Text('Picture Cache'),
-                  pinned: true,
-                  expandedHeight: 50.0,
-                  forceElevated: innerBoxIsScrolled,
+          // pinned: true,
+          // expandedHeight: 50.0,
+          // forceElevated: innerBoxIsScrolled,
           bottom: TabBar(
             tabs: kTabNames.map((String name) => Tab(text: name)).toList(),
           ),
         ),
-              ),
-            ];
-          },
         body: TabBarView(
+          key: const Key('tabbar_view'), // this key is used by the driver test
           children: kTabNames.map((String name) {
             return SafeArea(
               top: false,
               bottom: false,
               child: Builder(
                 builder: (BuildContext context) {
-                    return VerticalList();
+                  return ListView.builder(
+                    itemBuilder: (BuildContext context, int index) => ListItem(index: index),
+                  );
                 },
               ),
             );
           }).toList(),
         ),
       ),
-      ),
-    );
-  }
-}
-
-class VerticalList extends StatelessWidget {
-  static const int kItemCount = 100;
-
-  @override
-  Widget build(BuildContext context) {
-    return CustomScrollView(
-      slivers: <Widget>[
-        SliverOverlapInjector(
-          // This is the flip side of the SliverOverlapAbsorber above.
-          handle: NestedScrollView.sliverOverlapAbsorberHandleFor(context),
-        ),
-        SliverList(
-          delegate: SliverChildBuilderDelegate(
-                (BuildContext context, int index) => ListItem(index: index),
-            childCount: kItemCount,
-          ),
-        ),
-      ],
     );
   }
 }

dev/benchmarks/macrobenchmarks/test_driver/picture_cache_perf_test.dart

@@ -13,9 +13,10 @@ void main() {
     kPictureCacheRouteName,
     pageDelay: const Duration(seconds: 1),
     driverOps: (FlutterDriver driver) async {
-      final SerializableFinder nestedScroll = find.byValueKey('nested-scroll');
+      final SerializableFinder tabBarView = find.byValueKey('tabbar_view');
       Future<void> _scrollOnce(double offset) async {
-        await driver.scroll(nestedScroll, offset, 0.0, const Duration(milliseconds: 300));
+        // Technically it's not scrolling but moving
+        await driver.scroll(tabBarView, offset, 0.0, const Duration(milliseconds: 300));
         await Future<void>.delayed(const Duration(milliseconds: 500));
       }
       for (int i = 0; i < 3; i += 1) {