Migrate to the New Material Buttons (#668)

experimental/desktop_photo_search/lib/src/widgets/photo_search_dialog.dart

@@ -50,13 +50,13 @@ class _PhotoSearchDialogState extends State<PhotoSearchDialog> {
           },
         ),
         actions: <Widget>[
-          FlatButton(
+          TextButton(
             onPressed: () {
               Navigator.of(context).pop();
             },
             child: Text('Cancel'.toUpperCase()),
           ),
-          FlatButton(
+          TextButton(
             onPressed: _searchEnabled
                 ? () {
                     widget.callback(_controller.text);

experimental/desktop_photo_search/test/widget_test.dart

@@ -90,7 +90,7 @@ class PhotoSearchModelTester extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     return MaterialApp(
-      home: FlatButton(
+      home: TextButton(
         key: fabKey,
         onPressed: () async {
           await Provider.of<PhotoSearchModel>(