Revert of Third attempt to land change to remove NativeViewportService and

mojo/services/public/interfaces/native_viewport/native_viewport.mojom

Index: mojo/services/public/interfaces/native_viewport/native_viewport.mojom
diff --git a/mojo/services/public/interfaces/native_viewport/native_viewport.mojom b/mojo/services/public/interfaces/native_viewport/native_viewport.mojom
index 6c9fd199a93070aa8de2fa734f8d717eba0c763e..a182a1493c053d1bbd64403ba017297e653ee095 100644
--- a/mojo/services/public/interfaces/native_viewport/native_viewport.mojom
+++ b/mojo/services/public/interfaces/native_viewport/native_viewport.mojom
@@ -26,11 +26,4 @@
   OnEvent(Event event) => ();
 };
 
-// Connect to this interface before any other connections are made and call
-// UseTestConfig(), blocking on the reply. This will ensure that the correct
-// global initialization is done before subsequent connections.
-interface NativeViewportConfig {
-  UseTestConfig() => ();
-};
-
 }