Add descriptions to unreached_func calls to improve failure output.

Change-Id: I9b07e71d272fbeb2a701b5702a6ae6affff16290
Bug: 1322072
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3631798
Reviewed-by: Hiroshige Hayashizaki <hiroshige@chromium.org>
Commit-Queue: Fergal Daly <fergal@chromium.org>
Reviewed-by: Darren Willis <djw@chromium.org>
Reviewed-by: Yutaka Hirano <yhirano@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1000846}
diff --git a/fetch/content-type/script.window.js b/fetch/content-type/script.window.js
index 88584ce..3159895 100644
--- a/fetch/content-type/script.window.js
+++ b/fetch/content-type/script.window.js
@@ -26,10 +26,10 @@
       script.onload = t.step_func_done(() => {
         assert_equals(self.stringFromExecutedScript, testData.encoding === "windows-1252" ? "€" : "€");
       });
-      script.onerror = t.unreached_func();
+      script.onerror = t.unreached_func("onerror");
     } else {
       script.onerror = t.step_func_done();
-      script.onload = t.unreached_func();
+      script.onload = t.unreached_func("onload");
     }
   }, (singleHeader ? "combined" : "separate") + " " + testData.contentType.join(" "));
 }