Use sliver-based scrolling in more places (#7893)

In particular, we now use ListView in the about dialog.

dev/benchmarks/complex_layout/lib/main.dart

@@ -52,24 +52,6 @@ class ComplexLayout extends StatefulWidget {
   static ComplexLayoutState of(BuildContext context) => context.ancestorStateOfType(const TypeMatcher<ComplexLayoutState>());
 }
 
-class FancyItemDelegate extends LazyBlockDelegate {
-  @override
-  Widget buildItem(BuildContext context, int index) {
-    if (index % 2 == 0)
-      return new FancyImageItem(index, key: new ValueKey<int>(index));
-    else
-      return new FancyGalleryItem(index, key: new ValueKey<int>(index));
-  }
-
-  @override
-  bool shouldRebuild(FancyItemDelegate oldDelegate) => false;
-
-  @override
-  double estimateTotalExtent(int firstIndex, int lastIndex, double minOffset, double firstStartOffset, double lastEndOffset) {
-    return double.INFINITY;
-  }
-}
-
 class ComplexLayoutState extends State<ComplexLayout> {
   @override
   Widget build(BuildContext context) {
@@ -91,10 +73,15 @@ class ComplexLayoutState extends State<ComplexLayout> {
       body: new Column(
         children: <Widget>[
           new Expanded(
-            child: new LazyBlock(
+            child: new ListView.builder(
               key: new Key('main-scroll'), // this key is used by the driver test
-              delegate: new FancyItemDelegate(),
-            )
+              itemBuilder: (BuildContext context, int index) {
+                if (index % 2 == 0)
+                  return new FancyImageItem(index, key: new ValueKey<int>(index));
+                else
+                  return new FancyGalleryItem(index, key: new ValueKey<int>(index));
+              },
+            ),
           ),
           new BottomBar(),
         ],

packages/flutter/lib/src/material/about.dart

@@ -447,15 +447,14 @@ class _LicensePageState extends State<LicensePage> {
       ),
       body: new DefaultTextStyle(
         style: Theme.of(context).textTheme.caption,
-        child: new Scrollbar(
-          child: new LazyBlock(
+        child: new Scrollbar2(
+          child: new ListView(
             padding: const EdgeInsets.symmetric(horizontal: 8.0, vertical: 12.0),
-            delegate: new LazyBlockChildren(
-              children: contents
-            )
-          )
-        )
-      )
+            shrinkWrap: true,
+            children: contents,
+          ),
+        ),
+      ),
     );
   }
 }

packages/flutter/test/widgets/scroll_interaction_test.dart

@@ -7,29 +7,29 @@ import 'package:flutter/widgets.dart';
 
 void main() {
   testWidgets('Scroll flings twice in a row does not crash', (WidgetTester tester) async {
-    await tester.pumpWidget(new Block(
+    await tester.pumpWidget(new ListView(
       children: <Widget>[
         new Container(height: 100000.0)
       ]
     ));
 
-    ScrollableState scrollable =
-      tester.state<ScrollableState>(find.byType(Scrollable));
+    Scrollable2State scrollable =
+      tester.state<Scrollable2State>(find.byType(Scrollable2));
 
-    expect(scrollable.scrollOffset, equals(0.0));
+    expect(scrollable.position.pixels, equals(0.0));
 
     await tester.flingFrom(const Point(200.0, 300.0), const Offset(0.0, -200.0), 500.0);
     await tester.pump();
     await tester.pump(const Duration(seconds: 5));
 
-    expect(scrollable.scrollOffset, greaterThan(0.0));
+    expect(scrollable.position.pixels, greaterThan(0.0));
 
-    double oldOffset = scrollable.scrollOffset;
+    double oldOffset = scrollable.position.pixels;
 
     await tester.flingFrom(const Point(200.0, 300.0), const Offset(0.0, -200.0), 500.0);
     await tester.pump();
     await tester.pump(const Duration(seconds: 5));
 
-    expect(scrollable.scrollOffset, greaterThan(oldOffset));
+    expect(scrollable.position.pixels, greaterThan(oldOffset));
   });
 }

packages/flutter/test/widgets/scrollable_list_with_inherited_test.dart

@@ -21,8 +21,8 @@ Widget buildCard(BuildContext context, int index) {
 }
 
 Widget buildFrame() {
-  return new LazyBlock(
-    delegate: new LazyBlockBuilder(builder: buildCard)
+  return new ListView.builder(
+    itemBuilder: buildCard,
   );
 }