Auto merge of #12076 - jdm:font-load, r=pcwalton

Make font template data load fallible

Remove a TODO around dealing with a failed file operation.

Can we write an automated test for this? I don't really know what font template data is, but this failure seems to be fontconfig-specific...

---
- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix #12037
- [ ] There are tests for these changes OR
- [ ] These changes do not require tests because _____

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components/gfx/platform/macos/font_template.rs

@@ -12,7 +12,7 @@ use serde::de::{Error, Visitor};
 use std::borrow::ToOwned;
 use std::collections::HashMap;
 use std::fs::File;
-use std::io::Read;
+use std::io::{Read, Error as IoError};
 use std::ops::Deref;
 use std::sync::Mutex;
 use string_cache::Atom;
@@ -41,12 +41,12 @@ unsafe impl Send for FontTemplateData {}
 unsafe impl Sync for FontTemplateData {}
 
 impl FontTemplateData {
-    pub fn new(identifier: Atom, font_data: Option<Vec<u8>>) -> FontTemplateData {
-        FontTemplateData {
+    pub fn new(identifier: Atom, font_data: Option<Vec<u8>>) -> Result<FontTemplateData, IoError> {
+        Ok(FontTemplateData {
             ctfont: CachedCTFont(Mutex::new(HashMap::new())),
             identifier: identifier.to_owned(),
             font_data: font_data
-        }
+        })
     }
 
     /// Retrieves the Core Text font instance, instantiating it if necessary.