Fix the scrolling layout deviation of CupertinoActionSheet (#149439)

This PR changes `CupertinoActionSheet`'s layout algorithm, so that the actions section always has the lower priority to take up vertical space with a fixed minimum height of 84.3 px. 

Currently `CupertinoActionSheet` uses a very complicated rule the determine the sizes of various sections:
1. If there are <= 3 buttons and a cancel button, or 1 button without a cancel button, then the actions section should never scroll.
2. Otherwise, then the content section takes priority to take over spaces but must leave at least `actionsMinHeight` for the actions section.

This has been the case since `CupertinoActionSheet` was first introduced ([first PR](flutter/flutter#19232)). Maybe it was the case before, but it's no longer reproducible on the latest SwiftUI.

The following images for comparison (left to right: Current Flutter, Flutter after this PR, SwiftUI). Pay attention to whether the actions section scrolls. (There are also some height/padding issues, which will be fixed in a future PR.)

Two buttons:
<img width="1006" alt="image" src="https:/flutter/flutter/assets/1596656/27ca5df7-1140-4bfd-9a5f-3b5972632c92">

Three buttons:
<img width="1025" alt="image" src="https:/flutter/flutter/assets/1596656/f2be6a5c-1713-4ffe-9705-27a668e5133d">

Four buttons:
<img width="1024" alt="image" src="https:/flutter/flutter/assets/1596656/5b90d9f4-11ed-4c04-bdea-0b81b1d2bd3d">

In SwiftUI, the action section seems to always have a minimum height of ~84 pixels regardless of the number of buttons. Therefore this PR also fixed this behavior, and adjusted the related tests.

packages/flutter/lib/src/cupertino/dialog.dart

@@ -631,7 +631,6 @@ class _CupertinoActionSheetState extends State<CupertinoActionSheet> {
  child: _ActionSheetMainSheet(
  scrollController: _effectiveActionScrollController,
  hasContent: hasContent,
- hasCancelButton: widget.cancelButton != null,
  contentSection: Builder(builder: _buildContent),
  actions: widget.actions,
  dividerColor: _kActionSheetButtonDividerColor,
@@ -918,15 +917,13 @@ class _ActionSheetMainSheet extends StatefulWidget {
  required this.scrollController,
  required this.actions,
  required this.hasContent,
- required this.hasCancelButton,
  required this.contentSection,
  required this.dividerColor,
  });
 
  final ScrollController? scrollController;
  final List<Widget>? actions;
  final bool hasContent;
- final bool hasCancelButton;
  final Widget contentSection;
  final Color dividerColor;
 
@@ -980,25 +977,16 @@ class _ActionSheetMainSheetState extends State<_ActionSheetMainSheet> {
 
  bool _hasActions() => (widget.actions?.length ?? 0) != 0;
 
- // If `aggressivelyLayout` is true, then the content section takes as much
- // space as needed up to `maxHeight`.
- //
- // If `aggressivelyLayout` is false, then the content section takes whatever
- // space is left by the other sections.
- Widget _buildContent({
- required bool hasActions,
- required bool aggressivelyLayout,
- required double maxHeight,
- }) {
- if (hasActions && aggressivelyLayout) {
- return ConstrainedBox(
- constraints: BoxConstraints(
- maxHeight: maxHeight,
- ),
+ Widget _buildContent({required bool hasActions, required double maxHeight}) {
+ if (!hasActions) {
+ return Flexible(
  child: widget.contentSection,
  );
  }
- return Flexible(
+ return ConstrainedBox(
+ constraints: BoxConstraints(
+ maxHeight: maxHeight,
+ ),
  child: widget.contentSection,
  );
  }
@@ -1019,16 +1007,8 @@ class _ActionSheetMainSheetState extends State<_ActionSheetMainSheet> {
 
  @override
  Widget build(BuildContext context) {
- // The layout rule:
- //
- // 1. If there are <= 3 buttons and a cancel button, or 1 button without a
- // cancel button, then the actions section should never scroll.
- // 2. Otherwise, then the content section takes priority to take over spaces
- // but must leave at least `actionsMinHeight` for the actions section.
- final int numActions = widget.actions?.length ?? 0;
- final bool actionsMightScroll =
- (numActions > 3 && widget.hasCancelButton) ||
- (numActions > 1 && !widget.hasCancelButton) ;
+ // The content section takes priority for vertical space but must leave at
+ // least `_kActionSheetActionsSectionMinHeight` for the actions section.
  final Color backgroundColor = CupertinoDynamicColor.resolve(_kActionSheetBackgroundColor, context);
  return LayoutBuilder(
  builder: (BuildContext context, BoxConstraints constraints) {
@@ -1037,7 +1017,6 @@ class _ActionSheetMainSheetState extends State<_ActionSheetMainSheet> {
  children: <Widget>[
  _buildContent(
  hasActions: _hasActions(),
- aggressivelyLayout: actionsMightScroll,
  maxHeight: constraints.maxHeight - _kActionSheetActionsSectionMinHeight - _kDividerThickness,
  ),
  if (widget.hasContent && _hasActions())
@@ -1046,7 +1025,6 @@ class _ActionSheetMainSheetState extends State<_ActionSheetMainSheet> {
  hidden: false,
  ),
  Flexible(
- flex: actionsMightScroll ? 1 : 0,
  child: Stack(
  children: <Widget>[
  Positioned.fill(

packages/flutter/test/cupertino/action_sheet_test.dart

@@ -719,7 +719,7 @@ void main() {
  await tester.tap(find.text('Go'));
  await tester.pump();
 
- expect(findScrollableActionsSectionRenderBox(tester).size.height, moreOrLessEquals(112.3));
+ expect(findScrollableActionsSectionRenderBox(tester).size.height, moreOrLessEquals(84.3));
  });
 
  testWidgets('3 action buttons with cancel button', (WidgetTester tester) async {
@@ -753,7 +753,7 @@ void main() {
  await tester.tap(find.text('Go'));
  await tester.pump();
 
- expect(findScrollableActionsSectionRenderBox(tester).size.height, moreOrLessEquals(168.6));
+ expect(findScrollableActionsSectionRenderBox(tester).size.height, moreOrLessEquals(84.3));
  });
 
  testWidgets('4+ action buttons with cancel button', (WidgetTester tester) async {