Expose a color property to CloseButton (#49256)

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

@@ -128,13 +128,20 @@ class BackButton extends StatelessWidget {
 ///  * [IconButton], to create other material design icon buttons.
 class CloseButton extends StatelessWidget {
   /// Creates a Material Design close button.
-  const CloseButton({ Key key }) : super(key: key);
+  const CloseButton({ Key key, this.color }) : super(key: key);
+
+  /// The color to use for the icon.
+  ///
+  /// Defaults to the [IconThemeData.color] specified in the ambient [IconTheme],
+  /// which usually matches the ambient [Theme]'s [ThemeData.iconTheme].
+  final Color color;
 
   @override
   Widget build(BuildContext context) {
     assert(debugCheckHasMaterialLocalizations(context));
     return IconButton(
       icon: const Icon(Icons.close),
+      color: color,
       tooltip: MaterialLocalizations.of(context).closeButtonTooltip,
       onPressed: () {
         Navigator.maybePop(context);

packages/flutter/test/material/back_button_test.dart

@@ -69,7 +69,6 @@ void main() {
     final Key iOSKey = UniqueKey();
     final Key androidKey = UniqueKey();
 
-
     await tester.pumpWidget(
       MaterialApp(
         home: Column(
@@ -92,6 +91,24 @@ void main() {
     expect(iOSIcon == androidIcon, false);
   });
 
+  testWidgets('BackButton color', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      const MaterialApp(
+        home: Material(
+          child: BackButton(
+            color: Colors.blue,
+          ),
+        ),
+      ),
+    );
+
+    final RichText iconText = tester.firstWidget(find.descendant(
+        of: find.byType(BackButton),
+        matching: find.byType(RichText)
+    ));
+    expect(iconText.text.style.color, Colors.blue);
+  });
+
   testWidgets('BackButton semantics', (WidgetTester tester) async {
     final SemanticsHandle handle = tester.ensureSemantics();
     await tester.pumpWidget(
@@ -123,4 +140,22 @@ void main() {
     ));
     handle.dispose();
   });
+
+  testWidgets('CloseButton color', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      const MaterialApp(
+        home: Material(
+          child: CloseButton(
+            color: Colors.red,
+          ),
+        ),
+      ),
+    );
+
+    final RichText iconText = tester.firstWidget(find.descendant(
+        of: find.byType(CloseButton),
+        matching: find.byType(RichText)
+    ));
+    expect(iconText.text.style.color, Colors.red);
+  });
 }