Support macOS video platform views (#1116)

## Summary

- enable `VideoRenderMode.platformView` on macOS in `VideoTrackRenderer`
- avoid texture-only resize assumptions by reading width/height from the
shared video renderer interface
- add a patch changeset for macOS platform video rendering support

## Validation

- `flutter analyze --no-pub`

Author: hiroshihorie

.changes/macos-video-platform-view

@@ -0,0 +1 @@
+patch type="fixed" "Support platform video rendering on macOS"

lib/src/widgets/video_track_renderer.dart

@@ -15,7 +15,7 @@
 import 'dart:async';
 import 'dart:math';
 
-import 'package:flutter/foundation.dart' show kIsWeb;
+import 'package:flutter/foundation.dart' show ValueListenable, kIsWeb;
 import 'package:flutter/material.dart';
 
 import 'package:flutter_webrtc/flutter_webrtc.dart' as rtc;
@@ -78,7 +78,7 @@ class VideoTrackRenderer extends StatefulWidget {
 
   /// Placeholder builder to display while the track is loading.
   ///
-  /// On iOS, this has no effect when [renderMode] is [VideoRenderMode.platformView].
+  /// On iOS and macOS, this has no effect when [renderMode] is [VideoRenderMode.platformView].
   final WidgetBuilder? placeholderBuilder;
 
   const VideoTrackRenderer(
@@ -107,9 +107,21 @@ class _VideoTrackRendererState extends State<VideoTrackRenderer> {
   // Used to compute visibility information
   late VideoTrackViewRegistration _viewRegistration;
 
-  Future<rtc.VideoRenderer> _initializeRenderer() async {
-    if (lkPlatformIs(PlatformType.iOS) && widget.renderMode == VideoRenderMode.platformView) {
-      return Null as Future<rtc.VideoRenderer>;
+  bool get _shouldUsePlatformView =>
+      widget.renderMode == VideoRenderMode.platformView &&
+      [PlatformType.iOS, PlatformType.macOS].contains(lkPlatform());
+
+  double? get _rendererAspectRatio {
+    final renderer = _renderer;
+    if (renderer != null && renderer is ValueListenable<rtc.RTCVideoValue>) {
+      return (renderer as ValueListenable<rtc.RTCVideoValue>).value.aspectRatio;
+    }
+    return null;
+  }
+
+  Future<rtc.VideoRenderer?> _initializeRenderer() async {
+    if (_shouldUsePlatformView) {
+      return null;
     }
     if (_renderer == null) {
       _renderer = rtc.RTCVideoRenderer();
@@ -192,7 +204,7 @@ class _VideoTrackRendererState extends State<VideoTrackRenderer> {
     _renderer?.onResize = () {
       if (mounted) {
         setState(() {
-          _aspectRatio = (_renderer as rtc.RTCVideoRenderer?)?.videoValue.aspectRatio;
+          _aspectRatio = _rendererAspectRatio;
         });
       }
     };
@@ -236,7 +248,7 @@ class _VideoTrackRendererState extends State<VideoTrackRenderer> {
         );
 
   Widget _videoRendererView() {
-    if (lkPlatformIs(PlatformType.iOS) && widget.renderMode == VideoRenderMode.platformView) {
+    if (_shouldUsePlatformView) {
       return rtc.RTCVideoPlatFormView(
         mirror: _shouldMirror(),
         objectFit: widget.fit.toRTCType(),
@@ -259,8 +271,7 @@ class _VideoTrackRendererState extends State<VideoTrackRenderer> {
   Widget _videoViewForNative() => FutureBuilder(
       future: _initializeRenderer(),
       builder: (context, snapshot) {
-        if ((snapshot.hasData && _renderer != null) ||
-            (lkPlatformIs(PlatformType.iOS) && widget.renderMode == VideoRenderMode.platformView)) {
+        if ((snapshot.hasData && _renderer != null) || _shouldUsePlatformView) {
           return Builder(
             key: _viewRegistration.key,
             builder: (ctx) {