macOS: ARC bridge casts for FlutterMetalTexture.user_data

shell/platform/darwin/macos/framework/Source/FlutterSurface.mm

@@ -52,21 +52,21 @@ - (instancetype)initWithSize:(CGSize)size device:(id<MTLDevice>)device {
   return self;
 }
 
-static void ReleaseSurface(void* surface) {
-  if (surface != nullptr) {
-    CFBridgingRelease(surface);
-  }
-}
-
 - (FlutterMetalTexture)asFlutterMetalTexture {
-  FlutterMetalTexture res;
-  memset(&res, 0, sizeof(FlutterMetalTexture));
-  res.struct_size = sizeof(FlutterMetalTexture);
-  res.texture = (__bridge void*)_texture;
-  res.texture_id = self.textureId;
-  res.user_data = (void*)CFBridgingRetain(self);
-  res.destruction_callback = ReleaseSurface;
-  return res;
+  return FlutterMetalTexture{
+      .struct_size = sizeof(FlutterMetalTexture),
+      .texture_id = self.textureId,
+      .texture = (__bridge void*)_texture,
+      // Retain for use in [FlutterSurface fromFlutterMetalTexture]. Released in
+      // destruction_callback.
+      .user_data = (__bridge_retained void*)self,
+      .destruction_callback =
+          [](void* user_data) {
+            // Balancing release for the retain when setting user_data above.
+            FlutterSurface* surface = (__bridge_transfer FlutterSurface*)user_data;
+            surface = nil;
+          },
+  };
 }
 
 + (FlutterSurface*)fromFlutterMetalTexture:(const FlutterMetalTexture*)texture {