Add PopupMenuButton.iconColor, PopupMenuTheme.iconSize and fix button icon using unexpected color propert (#132054)
fixes [PopupMenuButton uses color property for icon color](https://github.com/flutter/flutter/issues/127802)
fixes [`popup_menu_test.dart` lacks default icon color tests.](https://github.com/flutter/flutter/issues/132050)
### Description
- Add `PopupMenuButton..iconColor` and fix the PopupMenu button icon using an unexpected color property.
- Add the missing `PopupMenuTheme.iconSize`.
- Clean up some tests and minor improvements.
### Code sample
<details>
<summary>expand to view the code sample</summary>
```dart
import 'package:flutter/material.dart';
/// Flutter code sample for [PopupMenuButton].
// This is the type used by the popup menu below.
enum SampleItem { itemOne, itemTwo, itemThree }
void main() => runApp(const PopupMenuApp());
class PopupMenuApp extends StatelessWidget {
const PopupMenuApp({super.key});
@override
Widget build(BuildContext context) {
return MaterialApp(
theme: ThemeData(
popupMenuTheme: PopupMenuThemeData(
// iconSize: 75,
// iconColor: Colors.amber,
color: Colors.deepPurple[100],
),
),
home: const PopupMenuExample(),
);
}
}
class PopupMenuExample extends StatefulWidget {
const PopupMenuExample({super.key});
@override
State<PopupMenuExample> createState() => _PopupMenuExampleState();
}
class _PopupMenuExampleState extends State<PopupMenuExample> {
SampleItem? selectedMenu;
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(title: const Text('PopupMenuButton')),
body: Center(
child: PopupMenuButton<SampleItem>(
iconSize: 75,
// iconColor: Colors.amber,
color: Colors.deepPurple[100],
initialValue: selectedMenu,
// Callback that sets the selected popup menu item.
onSelected: (SampleItem item) {
setState(() {
selectedMenu = item;
});
},
itemBuilder: (BuildContext context) => <PopupMenuEntry<SampleItem>>[
const PopupMenuItem<SampleItem>(
value: SampleItem.itemOne,
child: Text('Item 1'),
),
const PopupMenuItem<SampleItem>(
value: SampleItem.itemTwo,
child: Text('Item 2'),
),
const PopupMenuDivider(),
const CheckedPopupMenuItem<SampleItem>(
value: SampleItem.itemThree,
checked: true,
child: Text('Item 3'),
),
],
),
),
);
}
}
```
</details>
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