[quick_actions] Add const constructor (flutter#4131)

Author: Abhishek01039

packages/quick_actions/quick_actions/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 0.6.0+3
+
+* Added a `const` constructor for the `QuickActions` class, so the plugin will behave as documented in the  sample code mentioned in the [README.md](https://github.com/flutter/plugins/blob/59e16a556e273c2d69189b2dcdfa92d101ea6408/packages/quick_actions/quick_actions/README.md).
+
 ## 0.6.0+2
 
 * Migrate maven repository from jcenter to mavenCentral.

packages/quick_actions/quick_actions/lib/quick_actions.dart

@@ -11,6 +11,9 @@ export 'package:quick_actions_platform_interface/types/types.dart';
 
 /// Quick actions plugin.
 class QuickActions {
+  /// Creates a new instance of [QuickActions].
+  const QuickActions();
+
   /// Initializes this plugin.
   ///
   /// Call this once before any further interaction with the the plugin.

packages/quick_actions/quick_actions/pubspec.yaml

@@ -3,7 +3,7 @@ description: Flutter plugin for creating shortcuts on home screen, also known as
   Quick Actions on iOS and App Shortcuts on Android.
 repository: https://github.com/flutter/plugins/tree/master/packages/quick_actions
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+quick_actions%22
-version: 0.6.0+2
+version: 0.6.0+3
 
 environment:
   sdk: ">=2.12.0 <3.0.0"

packages/quick_actions/quick_actions/test/quick_actions_test.dart

@@ -16,16 +16,21 @@ void main() {
       QuickActionsPlatform.instance = MockQuickActionsPlatform();
     });
 
+    test('constructor() should return valid QuickActions instance', () {
+      const QuickActions quickActions = QuickActions();
+      expect(quickActions, isNotNull);
+    });
+
     test('initialize() PlatformInterface', () async {
-      QuickActions quickActions = QuickActions();
+      const QuickActions quickActions = QuickActions();
       QuickActionHandler handler = (type) {};
 
       await quickActions.initialize(handler);
       verify(QuickActionsPlatform.instance.initialize(handler)).called(1);
     });
 
     test('setShortcutItems() PlatformInterface', () {
-      QuickActions quickActions = QuickActions();
+      const QuickActions quickActions = QuickActions();
       QuickActionHandler handler = (type) {};
       quickActions.initialize(handler);
       quickActions.setShortcutItems([]);
@@ -35,7 +40,7 @@ void main() {
     });
 
     test('clearShortcutItems() PlatformInterface', () {
-      QuickActions quickActions = QuickActions();
+      const QuickActions quickActions = QuickActions();
       QuickActionHandler handler = (type) {};
 
       quickActions.initialize(handler);