Assert that arc end caps on canvases with root surface transformations are drawn correctly.

ci/licenses_golden/licenses_flutter

@@ -908,6 +908,7 @@ FILE: ../../../flutter/shell/platform/embedder/embedder_task_runner.cc
 FILE: ../../../flutter/shell/platform/embedder/embedder_task_runner.h
 FILE: ../../../flutter/shell/platform/embedder/embedder_thread_host.cc
 FILE: ../../../flutter/shell/platform/embedder/embedder_thread_host.h
+FILE: ../../../flutter/shell/platform/embedder/fixtures/arc_end_caps.png
 FILE: ../../../flutter/shell/platform/embedder/fixtures/compositor.png
 FILE: ../../../flutter/shell/platform/embedder/fixtures/compositor_root_surface_xformation.png
 FILE: ../../../flutter/shell/platform/embedder/fixtures/compositor_software.png

shell/platform/embedder/BUILD.gn

@@ -88,6 +88,7 @@ config("embedder_prefix_config") {
 test_fixtures("fixtures") {
   dart_main = "fixtures/main.dart"
   fixtures = [
+    "fixtures/arc_end_caps.png",
     "fixtures/compositor.png",
     "fixtures/compositor_root_surface_xformation.png",
     "fixtures/compositor_software.png",

shell/platform/embedder/fixtures/main.dart

@@ -620,3 +620,30 @@ void scene_with_no_container() {
   };
   window.scheduleFrame();
 }
+
+Picture CreateArcEndCapsPicture() {
+  PictureRecorder baseRecorder = PictureRecorder();
+  Canvas canvas = Canvas(baseRecorder);
+
+  var style = Paint()
+    ..strokeWidth = 12.0
+    ..style = PaintingStyle.stroke
+    ..strokeCap = StrokeCap.round
+    ..strokeJoin = StrokeJoin.miter;
+
+  style.color = Color.fromARGB(255, 255, 0, 0);
+  canvas.drawArc(Rect.fromLTRB(0.0, 0.0, 500.0, 500.0), 1.57, 1.0, false, style);
+
+  return baseRecorder.endRecording();
+
+}
+
+@pragma('vm:entry-point')
+void arc_end_caps_correct() {
+  window.onBeginFrame = (Duration duration) {
+    SceneBuilder builder = SceneBuilder();
+    builder.addPicture(Offset(0.0, 0.0), CreateArcEndCapsPicture());
+    window.render(builder.build());
+  };
+  window.scheduleFrame();
+}

shell/platform/embedder/tests/embedder_unittests.cc

@@ -3550,5 +3550,46 @@ TEST_F(EmbedderTest, SceneWithNoRootContainerIsAcceptable) {
   latch.Wait();
 }
 
+// Verifies that https://skia-review.googlesource.com/c/skia/+/259174 is pulled
+// into the engine.
+TEST_F(EmbedderTest, ArcEndCapsAreDrawnCorrectly) {
+  auto& context = GetEmbedderContext();
+
+  EmbedderConfigBuilder builder(context);
+  builder.SetOpenGLRendererConfig(SkISize::Make(800, 1024));
+  builder.SetCompositor();
+  builder.SetDartEntrypoint("arc_end_caps_correct");
+
+  const auto root_surface_transformation = SkMatrix()
+                                               .preScale(1.0, -1.0)
+                                               .preTranslate(1024.0, -800.0)
+                                               .preRotate(90.0);
+
+  context.SetRootSurfaceTransformation(root_surface_transformation);
+
+  auto engine = builder.LaunchEngine();
+
+  fml::AutoResetWaitableEvent latch;
+  sk_sp<SkImage> scene_image;
+  context.SetNextSceneCallback([&](sk_sp<SkImage> scene) {
+    scene_image = std::move(scene);
+    latch.Signal();
+  });
+
+  ASSERT_TRUE(engine.is_valid());
+
+  FlutterWindowMetricsEvent event = {};
+  event.struct_size = sizeof(event);
+  event.width = 1024;
+  event.height = 800;
+  event.pixel_ratio = 1.0;
+  ASSERT_EQ(FlutterEngineSendWindowMetricsEvent(engine.get(), &event),
+            kSuccess);
+
+  latch.Wait();
+
+  ASSERT_TRUE(ImageMatchesFixture("arc_end_caps.png", scene_image));
+}
+
 }  // namespace testing
 }  // namespace flutter