[PresentationAPI] Implementing send() from WebPresentationClient to the PresentationService.

content/browser/presentation/presentation_service_impl.cc

Index: content/browser/presentation/presentation_service_impl.cc
diff --git a/content/browser/presentation/presentation_service_impl.cc b/content/browser/presentation/presentation_service_impl.cc
index 9e2fd22e9c8c59971ce8f898b92864e220704a2e..dc9765d9e5c580cffc40cfb6346856129c0865a1 100644
--- a/content/browser/presentation/presentation_service_impl.cc
+++ b/content/browser/presentation/presentation_service_impl.cc
@@ -300,6 +300,14 @@ void PresentationServiceImpl::SetDefaultPresentationURL(
   DoSetDefaultPresentationUrl(new_default_url, default_presentation_id);
 }
 
+void PresentationServiceImpl::SendStringMessage(
+    const mojo::String& presentation_url,
+    const mojo::String& presentation_id,
+    const mojo::String& message,
+    const SendMessageMojoCallback& callback) {
+  NOTIMPLEMENTED();
+}
+
 void PresentationServiceImpl::CloseSession(
     const mojo::String& presentation_url,
     const mojo::String& presentation_id) {