mustash: Break dependency of //ash/public/interfaces on //ash

ash/public/cpp/BUILD.gn

Index: ash/public/cpp/BUILD.gn
diff --git a/services/file/public/cpp/BUILD.gn b/ash/public/cpp/BUILD.gn
similarity index 72%
copy from services/file/public/cpp/BUILD.gn
copy to ash/public/cpp/BUILD.gn
index f341a18b19af81ef3555e0516a57d41519a3b99b..ea64e0fbe9c48e6a9f8851c76a72ade685b08f6a 100644
--- a/services/file/public/cpp/BUILD.gn
+++ b/ash/public/cpp/BUILD.gn
@@ -2,9 +2,9 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+# C++ headers and sources that can be used outside ash.
 source_set("cpp") {
   sources = [
-    "constants.cc",
-    "constants.h",
+    "shelf_types.h",
   ]
 }