Updated the About dialog to use the new button API. (#62075)

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

@@ -19,7 +19,6 @@ import 'card.dart';
 import 'constants.dart';
 import 'debug.dart';
 import 'dialog.dart';
-import 'flat_button.dart';
 import 'floating_action_button.dart';
 import 'floating_action_button_location.dart';
 import 'ink_decoration.dart';
@@ -31,6 +30,7 @@ import 'page_transitions_theme.dart';
 import 'progress_indicator.dart';
 import 'scaffold.dart';
 import 'scrollbar.dart';
+import 'text_button.dart';
 import 'text_theme.dart';
 import 'theme.dart';
 
@@ -97,7 +97,7 @@ import 'theme.dart';
 ///        ),
 ///      ),
 ///      body: Center(
-///        child: RaisedButton(
+///        child: ElevatedButton(
 ///          child: Text('Show About Example'),
 ///          onPressed: () {
 ///            showAboutDialog(
@@ -406,7 +406,7 @@ class AboutDialog extends StatelessWidget {
         ],
       ),
       actions: <Widget>[
-        FlatButton(
+        TextButton(
           child: Text(MaterialLocalizations.of(context).viewLicensesButtonLabel),
           onPressed: () {
             showLicensePage(
@@ -418,7 +418,7 @@ class AboutDialog extends StatelessWidget {
             );
           },
         ),
-        FlatButton(
+        TextButton(
           child: Text(MaterialLocalizations.of(context).closeButtonLabel),
           onPressed: () {
             Navigator.pop(context);

packages/flutter/test/material/about_test.dart

@@ -358,7 +358,7 @@ void main() {
             onGenerateRoute: (RouteSettings settings) {
               return PageRouteBuilder<dynamic>(
                 pageBuilder: (BuildContext context, _, __) {
-                  return RaisedButton(
+                  return ElevatedButton(
                     onPressed: () {
                       showLicensePage(
                         context: context,
@@ -376,7 +376,7 @@ void main() {
     ));
 
     // Open the dialog.
-    await tester.tap(find.byType(RaisedButton));
+    await tester.tap(find.byType(ElevatedButton));
 
     expect(rootObserver.licensePageCount, 0);
     expect(nestedObserver.licensePageCount, 1);
@@ -396,7 +396,7 @@ void main() {
             onGenerateRoute: (RouteSettings settings) {
               return PageRouteBuilder<dynamic>(
                 pageBuilder: (BuildContext context, _, __) {
-                  return RaisedButton(
+                  return ElevatedButton(
                     onPressed: () {
                       showLicensePage(
                         context: context,
@@ -415,7 +415,7 @@ void main() {
     ));
 
     // Open the dialog.
-    await tester.tap(find.byType(RaisedButton));
+    await tester.tap(find.byType(ElevatedButton));
 
     expect(rootObserver.licensePageCount, 1);
     expect(nestedObserver.licensePageCount, 0);
@@ -432,7 +432,7 @@ void main() {
         onGenerateRoute: (RouteSettings settings) {
           return MaterialPageRoute<dynamic>(
             builder: (BuildContext context) {
-              return RaisedButton(
+              return ElevatedButton(
                 onPressed: () {
                   showAboutDialog(
                     context: context,
@@ -448,7 +448,7 @@ void main() {
     ));
 
     // Open the dialog.
-    await tester.tap(find.byType(RaisedButton));
+    await tester.tap(find.byType(ElevatedButton));
 
     expect(rootObserver.dialogCount, 1);
     expect(nestedObserver.dialogCount, 0);
@@ -465,7 +465,7 @@ void main() {
         onGenerateRoute: (RouteSettings settings) {
           return MaterialPageRoute<dynamic>(
             builder: (BuildContext context) {
-              return RaisedButton(
+              return ElevatedButton(
                 onPressed: () {
                   showAboutDialog(
                     context: context,
@@ -482,7 +482,7 @@ void main() {
     ));
 
     // Open the dialog.
-    await tester.tap(find.byType(RaisedButton));
+    await tester.tap(find.byType(ElevatedButton));
 
     expect(rootObserver.dialogCount, 0);
     expect(nestedObserver.dialogCount, 1);
@@ -515,7 +515,7 @@ void main() {
         onGenerateRoute: (RouteSettings settings) {
           return MaterialPageRoute<dynamic>(
             builder: (BuildContext context) {
-              return RaisedButton(
+              return ElevatedButton(
                 onPressed: () {
                   showAboutDialog(
                     context: context,