SkiaWindowPerfomanceTest. Fix compilation issue

samples/SkijaInjectSample/src/test/kotlin/org/jetbrains/skiko/SkiaWindowPerformanceTest.kt

@@ -44,9 +44,7 @@ native crash in SkiaWindowTest "render single window"
 //            .popStyle()
 //            .build()
 
-    @Test
-    fun `FPS is near display refresh rate (multiple windows)`() = swingTest {
-        class TestWindow(
+    private class TestWindow(
         width: Int,
         height: Int,
         private val frameCount: Int,
@@ -126,12 +124,14 @@ native crash in SkiaWindowTest "render single window"
         }
     }
 
-        suspend fun awaitFrameCollection(windows: List<TestWindow>) {
+    private suspend fun awaitFrameCollection(windows: List<TestWindow>) {
         while (!windows.all(TestWindow::isCollected)) {
             delay(100)
         }
     }
 
+    @Test
+    fun `FPS is near display refresh rate (multiple windows)`() = swingTest {
         val windows = (1..3).map { index ->
             TestWindow(width = 40, height = 20, frameCount = 300, deviatedTerminalCount = 10).apply {
                 location = Point((index + 1) * 200, 200)