Revert "Removed ButtonBar from AlertDialog (#75676)" (#75873)

This reverts commit 705cebb239.

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

@@ -424,8 +424,13 @@ class AlertDialog extends StatelessWidget {
   /// This is different from [actionsPadding], which defines the padding
   /// between the entire button bar and the edges of the dialog.
   ///
-  /// If this property is null, then it will default to
+  /// If this property is null, then it will use the surrounding
+  /// [ButtonBarThemeData.buttonPadding]. If that is null, it will default to
   /// 8.0 logical pixels on the left and right.
+  ///
+  /// See also:
+  ///
+  /// * [ButtonBar], which [actions] configures to lay itself out.
   final EdgeInsetsGeometry? buttonPadding;
 
   /// {@macro flutter.material.dialog.backgroundColor}
@@ -533,18 +538,13 @@ class AlertDialog extends StatelessWidget {
 
 
     if (actions != null) {
-      final double spacing = (buttonPadding?.horizontal ?? 16) / 2;
       actionsWidget = Padding(
         padding: actionsPadding,
-        child: Container(
-          alignment: AlignmentDirectional.centerEnd,
-          padding: EdgeInsets.all(spacing),
-          child: OverflowBar(
-            spacing: spacing,
-            overflowDirection: actionsOverflowDirection ?? VerticalDirection.down,
-            overflowSpacing: actionsOverflowButtonSpacing ?? 0,
-            children: actions!,
-          ),
+        child: ButtonBar(
+          buttonPadding: buttonPadding,
+          overflowDirection: actionsOverflowDirection,
+          overflowButtonSpacing: actionsOverflowButtonSpacing,
+          children: actions!,
         ),
       );
     }

packages/flutter/test/material/dialog_test.dart

@@ -46,13 +46,6 @@ RenderParagraph _getTextRenderObjectFromDialog(WidgetTester tester, String text)
   return tester.element<StatelessElement>(find.descendant(of: find.byType(Dialog), matching: find.text(text))).renderObject! as RenderParagraph;
 }
 
-// What was the AlertDialog's ButtonBar when many of these tests were written,
-// is now a Container with an OverflowBar child. The Container's size and location
-// match the original ButtonBar's size and location.
-Finder _findButtonBar() {
-  return find.ancestor(of: find.byType(OverflowBar), matching: find.byType(Container)).first;
-}
-
 const ShapeBorder _defaultDialogShape = RoundedRectangleBorder(borderRadius: BorderRadius.all(Radius.circular(4.0)));
 
 void main() {
@@ -502,7 +495,7 @@ void main() {
         matching: find.byType(Material),
       ).first,
     );
-    final Size actionsSize = tester.getSize(_findButtonBar());
+    final Size actionsSize = tester.getSize(find.byType(ButtonBar));
 
     expect(actionsSize.width, dialogSize.width);
   });
@@ -536,7 +529,7 @@ void main() {
         matching: find.byType(Material),
       ).first,
     );
-    final Size actionsSize = tester.getSize(_findButtonBar());
+    final Size actionsSize = tester.getSize(find.byType(ButtonBar));
 
     expect(actionsSize.width, dialogSize.width - (30.0 * 2));
   });
@@ -579,25 +572,25 @@ void main() {
     // First button
     expect(
       tester.getTopRight(find.byKey(key1)).dy,
-      tester.getTopRight(_findButtonBar()).dy + 8.0,
+      tester.getTopRight(find.byType(ButtonBar)).dy + 8.0,
     ); // top
     expect(
       tester.getBottomRight(find.byKey(key1)).dy,
-      tester.getBottomRight(_findButtonBar()).dy - 8.0,
+      tester.getBottomRight(find.byType(ButtonBar)).dy - 8.0,
     ); // bottom
 
     // Second button
     expect(
       tester.getTopRight(find.byKey(key2)).dy,
-      tester.getTopRight(_findButtonBar()).dy + 8.0,
+      tester.getTopRight(find.byType(ButtonBar)).dy + 8.0,
     ); // top
     expect(
       tester.getBottomRight(find.byKey(key2)).dy,
-      tester.getBottomRight(_findButtonBar()).dy - 8.0,
+      tester.getBottomRight(find.byType(ButtonBar)).dy - 8.0,
     ); // bottom
     expect(
       tester.getBottomRight(find.byKey(key2)).dx,
-      tester.getBottomRight(_findButtonBar()).dx - 8.0,
+      tester.getBottomRight(find.byType(ButtonBar)).dx - 8.0,
     ); // right
   });
 
@@ -643,25 +636,25 @@ void main() {
     // First button
     expect(
       tester.getTopRight(find.byKey(key1)).dy,
-      tester.getTopRight(_findButtonBar()).dy + ((10.0 + 20.0) / 2),
+      tester.getTopRight(find.byType(ButtonBar)).dy + ((10.0 + 20.0) / 2),
     ); // top
     expect(
       tester.getBottomRight(find.byKey(key1)).dy,
-      tester.getBottomRight(_findButtonBar()).dy - ((10.0 + 20.0) / 2),
+      tester.getBottomRight(find.byType(ButtonBar)).dy - ((10.0 + 20.0) / 2),
     ); // bottom
 
     // Second button
     expect(
       tester.getTopRight(find.byKey(key2)).dy,
-      tester.getTopRight(_findButtonBar()).dy + ((10.0 + 20.0) / 2),
+      tester.getTopRight(find.byType(ButtonBar)).dy + ((10.0 + 20.0) / 2),
     ); // top
     expect(
       tester.getBottomRight(find.byKey(key2)).dy,
-      tester.getBottomRight(_findButtonBar()).dy - ((10.0 + 20.0) / 2),
+      tester.getBottomRight(find.byType(ButtonBar)).dy - ((10.0 + 20.0) / 2),
     ); // bottom
     expect(
       tester.getBottomRight(find.byKey(key2)).dx,
-      tester.getBottomRight(_findButtonBar()).dx - ((10.0 + 20.0) / 2),
+      tester.getBottomRight(find.byType(ButtonBar)).dx - ((10.0 + 20.0) / 2),
     ); // right
   });
 
@@ -682,7 +675,7 @@ void main() {
     final Finder dialogFinder = find.descendant(of: find.byType(Dialog), matching: find.byType(Material)).first;
     final Finder titleFinder = find.byKey(titleKey);
     final Finder contentFinder = find.byKey(contentKey);
-    final Finder actionsFinder = _findButtonBar();
+    final Finder actionsFinder = find.byType(ButtonBar);
     final Finder childrenFinder = find.byKey(childrenKey);
 
     Future<void> openDialog(WidgetTester tester, Widget dialog, double textScaleFactor) async {