Add const to FadeScaleTransitionConfiguration

Author: mono0926

packages/animations/example/lib/fade_scale_transition.dart

@@ -67,7 +67,7 @@ class _FadeScaleTransitionDemoState extends State<FadeScaleTransitionDemo>
                   onPressed: () {
                     showModal<void>(
                       context: context,
-                      configuration: FadeScaleTransitionConfiguration(),
+                      configuration: const FadeScaleTransitionConfiguration(),
                       builder: (BuildContext context) {
                         return _ExampleAlertDialog();
                       },

packages/animations/lib/src/fade_scale_transition.dart

@@ -65,7 +65,7 @@ class FadeScaleTransitionConfiguration extends ModalConfiguration {
   /// scrim dismisses the modal. [barrierLabel] sets the semantic label for
   /// a dismissible barrier. [barrierDismissible] cannot be null. If
   /// [barrierDismissible] is true, the [barrierLabel] cannot be null.
-  FadeScaleTransitionConfiguration({
+  const FadeScaleTransitionConfiguration({
     Color barrierColor = Colors.black54,
     bool barrierDismissible = true,
     Duration transitionDuration = const Duration(milliseconds: 150),

packages/animations/lib/src/modal.dart

@@ -177,7 +177,7 @@ abstract class ModalConfiguration {
   /// duration of the transitions when the modal enters and exits the
   /// application. [transitionDuration] and [reverseTransitionDuration]
   /// cannot be null.
-  ModalConfiguration({
+  const ModalConfiguration({
     @required this.barrierColor,
     @required this.barrierDismissible,
     this.barrierLabel,

packages/animations/test/fade_scale_transition_test.dart

@@ -21,7 +21,7 @@ void main() {
                   onPressed: () {
                     showModal<void>(
                       context: context,
-                      configuration: FadeScaleTransitionConfiguration(),
+                      configuration: const FadeScaleTransitionConfiguration(),
                       builder: (BuildContext context) {
                         return const _FlutterLogoModal();
                       },
@@ -53,7 +53,7 @@ void main() {
                   onPressed: () {
                     showModal<void>(
                       context: context,
-                      configuration: FadeScaleTransitionConfiguration(),
+                      configuration: const FadeScaleTransitionConfiguration(),
                       builder: (BuildContext context) {
                         return _FlutterLogoModal(key: key);
                       },
@@ -121,7 +121,7 @@ void main() {
                   onPressed: () {
                     showModal<void>(
                       context: context,
-                      configuration: FadeScaleTransitionConfiguration(),
+                      configuration: const FadeScaleTransitionConfiguration(),
                       builder: (BuildContext context) {
                         return _FlutterLogoModal(key: key);
                       },
@@ -186,7 +186,7 @@ void main() {
                   onPressed: () {
                     showModal<void>(
                       context: context,
-                      configuration: FadeScaleTransitionConfiguration(),
+                      configuration: const FadeScaleTransitionConfiguration(),
                       builder: (BuildContext context) {
                         return _FlutterLogoModal(key: key);
                       },
@@ -287,7 +287,8 @@ void main() {
                       onPressed: () {
                         showModal<void>(
                           context: context,
-                          configuration: FadeScaleTransitionConfiguration(),
+                          configuration:
+                              const FadeScaleTransitionConfiguration(),
                           builder: (BuildContext context) {
                             return _FlutterLogoModal(
                               key: topKey,