Bug 1660989 [wpt PR 25224] - [fetch] Empty destination should be the empty string, not "empty", a=testonly

Automatic update from web-platform-tests
[fetch] Empty destination should be the empty string, not "empty"

As specified at [1],the empty destination should be the empty string,
not "empty". We use "empty" for the "sec-fetch-dest" header[2] though.

Fix the implementation and fix incorrect WPTs altogether.

1: https://fetch.spec.whatwg.org/#concept-request-destination
2: https://w3c.github.io/webappsec-fetch-metadata/#abstract-opdef-set-dest

Bug: 1121493
Change-Id: Ia86d716dd434c3b6b0e6f1914019fd6110a7ab8d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2374725
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Reviewed-by: Matt Falkenhagen <falken@chromium.org>
Commit-Queue: Yutaka Hirano <yhirano@chromium.org>
Cr-Commit-Position: refs/heads/master@{#801368}

--

wpt-commits: a05058d027c17c6863b1c3a4610dae0d2ab58876
wpt-pr: 25224

testing/web-platform/tests/fetch/api/request/request-structure.html

@@ -58,7 +58,7 @@
             break;
 
           case "destination":
-            defaultValue = "empty";
+            defaultValue = "";
             newValue = "worker";
             break;
 

testing/web-platform/tests/service-workers/service-worker/fetch-request-resources.https.html

@@ -117,7 +117,7 @@ function fetch_test(frame, url, mode, credentials,
       credentials: expected_credentials,
       redirect: 'follow',
       integrity: '',
-      destination: 'empty',
+      destination: '',
       message: `fetch (url:${actual_url} mode:${mode} ` +
                `credentials:${credentials})`
     };