[ios_platform_view] Only remove platform views from flutter view in reset.

shell/platform/darwin/ios/framework/Source/FlutterPlatformViews.mm

@@ -622,8 +622,8 @@ static bool ClipRRectContainsPlatformViewBoundingRect(const SkRRect& clip_rrect,
 }
 
 void FlutterPlatformViewsController::Reset() {
-  UIView* flutter_view = flutter_view_.get();
-  for (UIView* sub_view in [flutter_view subviews]) {
+  for (int64_t view_id : active_composition_order_) {
+    UIView* sub_view = root_views_[view_id].get();
     [sub_view removeFromSuperview];
   }
   root_views_.clear();

shell/platform/darwin/ios/framework/Source/FlutterPlatformViewsTest.mm

@@ -2896,5 +2896,70 @@ - (void)testDisposingViewInCompositionOrderDoNotCrash {
     XCTAssertNotNil(flutterPlatformViewsController->GetPlatformViewByID(1));
   }
 }
+- (void)testOnlyPlatformViewsAreRemovedWhenReset {
+  flutter::FlutterPlatformViewsTestMockPlatformViewDelegate mock_delegate;
+  auto thread_task_runner = CreateNewThread("FlutterPlatformViewsTest");
+  flutter::TaskRunners runners(/*label=*/self.name.UTF8String,
+                               /*platform=*/thread_task_runner,
+                               /*raster=*/thread_task_runner,
+                               /*ui=*/thread_task_runner,
+                               /*io=*/thread_task_runner);
+  auto flutterPlatformViewsController = std::make_shared<flutter::FlutterPlatformViewsController>();
+  auto platform_view = std::make_unique<flutter::PlatformViewIOS>(
+      /*delegate=*/mock_delegate,
+      /*rendering_api=*/flutter::IOSRenderingAPI::kSoftware,
+      /*platform_views_controller=*/flutterPlatformViewsController,
+      /*task_runners=*/runners);
+
+  FlutterPlatformViewsTestMockFlutterPlatformFactory* factory =
+      [[FlutterPlatformViewsTestMockFlutterPlatformFactory new] autorelease];
+  flutterPlatformViewsController->RegisterViewFactory(
+      factory, @"MockFlutterPlatformView",
+      FlutterPlatformViewGestureRecognizersBlockingPolicyEager);
+  FlutterResult result = ^(id result) {
+  };
+  flutterPlatformViewsController->OnMethodCall(
+      [FlutterMethodCall
+          methodCallWithMethodName:@"create"
+                         arguments:@{@"id" : @2, @"viewType" : @"MockFlutterPlatformView"}],
+      result);
+  UIView* mockFlutterView = [[[UIView alloc] initWithFrame:CGRectMake(0, 0, 500, 500)] autorelease];
+  flutterPlatformViewsController->SetFlutterView(mockFlutterView);
+  // Create embedded view params
+  flutter::MutatorsStack stack;
+  // Layer tree always pushes a screen scale factor to the stack
+  SkMatrix screenScaleMatrix =
+      SkMatrix::Scale([UIScreen mainScreen].scale, [UIScreen mainScreen].scale);
+  stack.PushTransform(screenScaleMatrix);
+  // Push a translate matrix
+  SkMatrix translateMatrix = SkMatrix::Translate(100, 100);
+  stack.PushTransform(translateMatrix);
+  SkMatrix finalMatrix;
+  finalMatrix.setConcat(screenScaleMatrix, translateMatrix);
+
+  auto embeddedViewParams =
+      std::make_unique<flutter::EmbeddedViewParams>(finalMatrix, SkSize::Make(300, 300), stack);
+
+  flutterPlatformViewsController->PrerollCompositeEmbeddedView(2, std::move(embeddedViewParams));
+  flutterPlatformViewsController->CompositeEmbeddedView(2);
+
+  // SKSurface is required if the root FlutterView is present.
+  const SkImageInfo image_info = SkImageInfo::MakeN32Premul(1000, 1000);
+  sk_sp<SkSurface> mock_sk_surface = SkSurface::MakeRaster(image_info);
+  flutter::SurfaceFrame::FramebufferInfo framebuffer_info;
+  auto mock_surface = std::make_unique<flutter::SurfaceFrame>(
+      std::move(mock_sk_surface), framebuffer_info,
+      [](const flutter::SurfaceFrame& surface_frame, flutter::DlCanvas* canvas) { return true; },
+      /*frame_size=*/SkISize::Make(800, 600));
+
+  flutterPlatformViewsController->SubmitFrame(nullptr, nullptr, std::move(mock_surface));
+
+  UIView* someView = [[[UIView alloc] init] autorelease];
+  [mockFlutterView addSubview:someView];
+
+  flutterPlatformViewsController->Reset();
+  XCTAssertEqual(mockFlutterView.subviews.count, 1u);
+  XCTAssertEqual(mockFlutterView.subviews.firstObject, someView);
+}
 
 @end