Replace base::File wrapping with typemapping.

components/font_service/public/interfaces/font_service.mojom

 // Copyright 2014 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.
 
 module font_service.mojom;
 
+import "mojo/common/common_custom_types.mojom";
+
 enum TypefaceSlant {
   ROMAN = 0,
   ITALIC = 1,
   OBLIQUE = 2,
 };
 
 struct TypefaceStyle {
   uint16 weight;
   uint8 width;
   TypefaceSlant slant;
@@ skipping 15 matching lines @@
 //
 // We still need to load fonts from within a sandboxed process. We set
 // up a service to match fonts and load them,
 interface FontService {
   // Returns the best match for |family_name| and |style|. On error, returns a
   // null |identity|.
   MatchFamilyName(string family_name, TypefaceStyle style) =>
       (FontIdentity? identity, string family_name, TypefaceStyle style);
 
   // Returns a handle to the raw font specified by |id_number|.
-  OpenStream(uint32 id_number) => (handle font_handle);
+  OpenStream(uint32 id_number) => (mojo.common.mojom.File? font_handle);
 };