New go generator shakedown.

mojom/generators/go/templates/encoding.go

Index: mojom/generators/go/templates/encoding.go
diff --git a/mojom/generators/go/templates/encoding.go b/mojom/generators/go/templates/encoding.go
index b002d15e85737e59a2be55069948f4086707103a..c201bf406a0f61f51fc0705102f4caa17050401e 100644
--- a/mojom/generators/go/templates/encoding.go
+++ b/mojom/generators/go/templates/encoding.go
@@ -15,8 +15,10 @@ const fieldEncodingTmplText = `
 if {{$info.Identifier}} == nil {
 {{- if $info.IsPointer -}}
 	encoder.WriteNullPointer()
-{{- else if $info.IsHandle -}}
+{{- else if or $info.IsInterfaceRequest $info.IsHandle -}}
 	encoder.WriteInvalidHandle()
+{{- else if $info.IsInterface -}}
+	encoder.WriteInvalidInterface()
 {{- end -}}
 } else {
 	{{ template "NonNullableFieldEncodingTmpl" $info }}
@@ -70,6 +72,10 @@ if {{$info.Identifier}} == nil {
 		return err
 	}
 }
+{{- else if $info.IsInterface -}}
+if err := encoder.{{$info.WriteFunction}}({{$info.Identifier}}.PassMessagePipe()); err != nil {
+	return err
+}
 {{- else if $info.IsArray -}}
 {{ $elInfo := $info.ElementEncodingInfo -}}
 encoder.StartArray(uint32(len({{$info.Identifier}})), {{$elInfo.BitSize}})