Send AndroidOverlay routing token from WMPI to AVDA.

media/base/routing_token_callback.h

Index: media/base/routing_token_callback.h
diff --git a/media/base/routing_token_callback.h b/media/base/routing_token_callback.h
index 5185a2ad61c7706be0026e5127cf8362d05de948..8dbeb4afb0b8de266ed3fcff7efbb8d5733ab6d9 100644
--- a/media/base/routing_token_callback.h
+++ b/media/base/routing_token_callback.h
@@ -14,6 +14,11 @@ namespace media {
 using RoutingTokenCallback =
     base::Callback<void(const base::UnguessableToken&)>;
 
+// Callback to register a RoutingTokenCallback with something that can provide
+// it.  For example, RenderFrame(Impl) will provide this, while WMPI can choose
+// to call it if it would like to be called back with a routing token.
+using RequestRoutingTokenCallback = base::Callback<void(RoutingTokenCallback)>;
+
 }  // namespace media
 
 #endif  // MEDIA_BASE_ANDROID_ROUTING_TOKEN_CALLBACK_H_