ui/platform_window: Introduce PlatformWindow for windowing primitives.

mojo/services/native_viewport/native_viewport.h

Index: mojo/services/native_viewport/native_viewport.h
diff --git a/mojo/services/native_viewport/native_viewport.h b/mojo/services/native_viewport/native_viewport.h
index ed0f1db183a858aae6eed042a2ddf9b0559a6d2b..d33f33ff889f30c198ffec659a7d3f17b3e7682b 100644
--- a/mojo/services/native_viewport/native_viewport.h
+++ b/mojo/services/native_viewport/native_viewport.h
@@ -57,12 +57,6 @@ class NativeViewport {
                                            NativeViewportDelegate* delegate);
 };
 
-#if defined(USE_X11)
-namespace test {
-MOJO_NATIVE_VIEWPORT_EXPORT void EnableTestNativeViewport();
-}
-#endif
-
 }  // namespace services
 }  // namespace mojo