[camera_web] Release the camera stream used to request video and audio permissions (#4342)

Author: bselwe

packages/camera/camera_web/CHANGELOG.md

@@ -1,3 +1,7 @@
+## NEXT
+
+* Fix cameraNotReadable error that prevented access to the camera on some Android devices.
+
 ## 0.2.0
 
 * Initial release, adapted from the Flutter [I/O Photobooth](https://photobooth.flutter.dev/) project.

packages/camera/camera_web/README.md

@@ -9,7 +9,7 @@ The web implementation of [`camera`][camera].
 ### Depend on the package
 
 This package is not an [endorsed implementation](https://flutter.dev/docs/development/packages-and-plugins/developing-packages#endorsed-federated-plugin)
-of the google_maps_flutter plugin yet, so you'll need to [add it explicitly](https://pub.dev/packages/camera_web/install).
+of the camera plugin yet, so you'll need to [add it explicitly](https://pub.dev/packages/camera_web/install).
 
 ## Example
 

packages/camera/camera_web/example/integration_test/camera_web_test.dart

@@ -110,6 +110,33 @@ void main() {
         ).called(1);
       });
 
+      testWidgets(
+          'releases the camera stream '
+          'used to request video and audio permissions', (tester) async {
+        final videoTrack = MockMediaStreamTrack();
+
+        var videoTrackStopped = false;
+        when(videoTrack.stop).thenAnswer((_) {
+          videoTrackStopped = true;
+        });
+
+        when(
+          () => cameraService.getMediaStreamForOptions(
+            CameraOptions(
+              audio: AudioConstraints(enabled: true),
+            ),
+          ),
+        ).thenAnswer(
+          (_) => Future.value(
+            FakeMediaStream([videoTrack]),
+          ),
+        );
+
+        final _ = await CameraPlatform.instance.availableCameras();
+
+        expect(videoTrackStopped, isTrue);
+      });
+
       testWidgets(
           'gets a video stream '
           'for a video input device', (tester) async {

packages/camera/camera_web/lib/src/camera_web.dart

@@ -89,12 +89,15 @@ class CameraPlugin extends CameraPlatform {
       }
 
       // Request video and audio permissions.
-      await _cameraService.getMediaStreamForOptions(
+      final cameraStream = await _cameraService.getMediaStreamForOptions(
         CameraOptions(
           audio: AudioConstraints(enabled: true),
         ),
       );
 
+      // Release the camera stream used to request video and audio permissions.
+      cameraStream.getVideoTracks().forEach((videoTrack) => videoTrack.stop());
+
       // Request available media devices.
       final devices = await mediaDevices.enumerateDevices();