Use ReadOnlyFile for returned fonts

Bug: 1130762
Change-Id: I0c003e2f5d17dbea3653f47508a4e47eff7cf61f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2458906Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Reviewed-by: Dominik Röttsches <drott@chromium.org>
Commit-Queue: Alex Gough <ajgo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#815691}

components/services/font/public/mojom/font_service.mojom

@@ -4,8 +4,8 @@
 
 module font_service.mojom;
 
-import "mojo/public/mojom/base/file.mojom";
 import "mojo/public/mojom/base/file_path.mojom";
+import "mojo/public/mojom/base/read_only_file.mojom";
 
 enum TypefaceSlant {
   ROMAN = 0,
@@ -63,7 +63,7 @@ interface FontService {
       (FontIdentity? identity, string family_name, TypefaceStyle style);
 
   // Returns a handle to the raw font specified by |id_number|.
-  OpenStream(uint32 id_number) => (mojo_base.mojom.File? font_handle);
+  OpenStream(uint32 id_number) => (mojo_base.mojom.ReadOnlyFile? font_handle);
 
   // Returns a fallback FontIdentity and Typeface style for the given character
   // and locale. If no fallback font can be found, returns a null identity.
@@ -93,5 +93,5 @@ interface FontService {
   // PPAPI Specific font call to match a font family and charset.
   MatchFontWithFallback(string family, bool is_bold, bool is_italic,
       uint32 charset, uint32 fallback_family_type) =>
-      (mojo_base.mojom.File? font_file_handle);
+      (mojo_base.mojom.ReadOnlyFile? font_file_handle);
 };