Require an explicit ServiceName annotation for interfaces in C++.

mojo/services/native_viewport/interfaces/native_viewport.mojom

Index: mojo/services/native_viewport/interfaces/native_viewport.mojom
diff --git a/mojo/services/native_viewport/interfaces/native_viewport.mojom b/mojo/services/native_viewport/interfaces/native_viewport.mojom
index 34654146fc1560d0ad1c496f9eb319e1c38b3e1c..a70db13f455f896a369efa1f60bc15d83414f7c9 100644
--- a/mojo/services/native_viewport/interfaces/native_viewport.mojom
+++ b/mojo/services/native_viewport/interfaces/native_viewport.mojom
@@ -23,6 +23,7 @@ struct SurfaceConfiguration {
   uint8 stencil_bits;
 };
 
+[ServiceName="mojo::NativeViewport"]
 interface NativeViewport {
   // TODO(sky): having a create function is awkward. Should there be a factory
   // to create the NativeViewport that takes the size?
@@ -47,6 +48,7 @@ interface NativeViewport {
   RequestMetrics() => (ViewportMetrics metrics);
 };
 
+[ServiceName="mojo::NativeViewportEventDispatcher"]
 interface NativeViewportEventDispatcher {
   OnEvent(Event event) => ();
 };