[video_player] Eliminate platform channel from mock platform (flutter#4588)

Author: stuartmorgan-g

packages/video_player/video_player/CHANGELOG.md

@@ -1,5 +1,8 @@
-## NEXT
+## 2.2.8
 
+* Changes the way the `VideoPlayerPlatform` instance is cached in the
+  controller, so that it's no longer impossible to change after the first use.
+* Updates unit tests to be self-contained.
 * Fixes integration tests.
 * Updates Android compileSdkVersion to 31.
 * Fixes a flaky integration test.

packages/video_player/video_player/lib/video_player.dart

@@ -17,10 +17,18 @@ export 'package:video_player_platform_interface/video_player_platform_interface.
 import 'src/closed_caption_file.dart';
 export 'src/closed_caption_file.dart';
 
-final VideoPlayerPlatform _videoPlayerPlatform = VideoPlayerPlatform.instance
-  // This will clear all open videos on the platform when a full restart is
-  // performed.
-  ..init();
+VideoPlayerPlatform? _lastVideoPlayerPlatform;
+
+VideoPlayerPlatform get _videoPlayerPlatform {
+  VideoPlayerPlatform currentInstance = VideoPlayerPlatform.instance;
+  if (_lastVideoPlayerPlatform != currentInstance) {
+    // This will clear all open videos on the platform when a full restart is
+    // performed.
+    currentInstance.init();
+    _lastVideoPlayerPlatform = currentInstance;
+  }
+  return currentInstance;
+}
 
 /// The duration, current position, buffering state, error state and settings
 /// of a [VideoPlayerController].

packages/video_player/video_player/pubspec.yaml

@@ -3,7 +3,7 @@ description: Flutter plugin for displaying inline video with other Flutter
   widgets on Android, iOS, and web.
 repository: https://github.com/flutter/plugins/tree/master/packages/video_player/video_player
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+video_player%22
-version: 2.2.7
+version: 2.2.8
 
 environment:
   sdk: ">=2.14.0 <3.0.0"
@@ -25,12 +25,6 @@ dependencies:
     sdk: flutter
   meta: ^1.3.0
   video_player_platform_interface: ^4.2.0
-  # The design on https://flutter.dev/go/federated-plugins was to leave
-  # this constraint as "any". We cannot do it right now as it fails pub publish
-  # validation, so we set a ^ constraint. The exact value doesn't matter since
-  # the constraints on the interface pins it.
-  # TODO(amirh): Revisit this (either update this part in the design or the pub tool).
-  # https://github.com/flutter/flutter/issues/46264
   video_player_web: ^2.0.0
   html: ^0.15.0
 

packages/video_player/video_player/test/video_player_initialization_test.dart

@@ -4,6 +4,7 @@
 
 import 'package:flutter_test/flutter_test.dart';
 import 'package:video_player/video_player.dart';
+import 'package:video_player_platform_interface/video_player_platform_interface.dart';
 
 import 'video_player_test.dart' show FakeVideoPlayerPlatform;
 
@@ -13,6 +14,7 @@ void main() {
   test('plugin initialized', () async {
     TestWidgetsFlutterBinding.ensureInitialized();
     FakeVideoPlayerPlatform fakeVideoPlayerPlatform = FakeVideoPlayerPlatform();
+    VideoPlayerPlatform.instance = fakeVideoPlayerPlatform;
 
     final VideoPlayerController controller = VideoPlayerController.network(
       'https://127.0.0.1',