Mojo bindings: Fix typemap includes.

url/mojo/origin.typemap

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 {
   "c++": {
     "url.mojom.Origin": {
       "typename": "url::Origin",
-      "headers": [
+      "public_headers": [
+        "url/origin.h"
+      ],
+      "traits_headers": [
         "url/mojo/origin_struct_traits.h"
       ]
     }
   }
 }