fix M2 InputDecorator suffix icon doesn't turn red on error (flutter#149161)

The suffixIcon of a TextField with an error now turns red like it should (on Material 2).

Author: bleroux

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

@@ -4570,7 +4570,7 @@ class _InputDecoratorDefaultsM2 extends InputDecorationTheme {
 
   @override
   TextStyle? get helperStyle => MaterialStateTextStyle.resolveWith((Set<MaterialState> states) {
-    final ThemeData themeData= Theme.of(context);
+    final ThemeData themeData = Theme.of(context);
     if (states.contains(MaterialState.disabled)) {
       return themeData.textTheme.bodySmall!.copyWith(color: Colors.transparent);
     }
@@ -4580,7 +4580,7 @@ class _InputDecoratorDefaultsM2 extends InputDecorationTheme {
 
   @override
   TextStyle? get errorStyle => MaterialStateTextStyle.resolveWith((Set<MaterialState> states) {
-    final ThemeData themeData= Theme.of(context);
+    final ThemeData themeData = Theme.of(context);
     if (states.contains(MaterialState.disabled)) {
       return themeData.textTheme.bodySmall!.copyWith(color: Colors.transparent);
     }
@@ -4630,6 +4630,9 @@ class _InputDecoratorDefaultsM2 extends InputDecorationTheme {
     if (states.contains(MaterialState.disabled) && !states.contains(MaterialState.focused)) {
       return Theme.of(context).disabledColor;
     }
+    if (states.contains(MaterialState.error)) {
+      return Theme.of(context).colorScheme.error;
+    }
     if (states.contains(MaterialState.focused)) {
       return Theme.of(context).colorScheme.primary;
     }

packages/flutter/test/material/input_decorator_test.dart

@@ -8885,6 +8885,29 @@ void main() {
       expect(tester.getTopRight(find.text('text')).dx, lessThanOrEqualTo(tester.getTopLeft(find.byIcon(Icons.satellite)).dx));
     });
 
+    testWidgets('Material2 - InputDecorator suffixIcon color in error state', (WidgetTester tester) async {
+      await tester.pumpWidget(
+        MaterialApp(
+          theme: ThemeData(useMaterial3: false),
+          home: Material(
+            child: TextField(
+              decoration: InputDecoration(
+                suffixIcon: IconButton(
+                  icon: const Icon(Icons.close),
+                  onPressed: () {},
+                ),
+                errorText: 'Error state',
+                filled: true,
+              ),
+            ),
+          ),
+        ),
+      );
+
+      final ThemeData theme = Theme.of(tester.element(find.byType(TextField)));
+      expect(getIconStyle(tester, Icons.close)?.color, theme.colorScheme.error);
+    });
+
     testWidgets('InputDecorator prefixIconConstraints/suffixIconConstraints', (WidgetTester tester) async {
       await tester.pumpWidget(
         buildInputDecoratorM2(