Make a WPT for renameSync fail if renameSync is not implemented.

As a missing function gives a TypeError, one of the WPTs for renameSync
would pass when renameSync is not implemented, which is
counterintuitive.

Bug: 914488
Change-Id: I4c16cf55723b772b0cba5c5c3acd376165e25591
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2310531Reviewed-by: Mike West <mkwst@chromium.org>
Commit-Queue: Richard Stotz <rstz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#790754}

third_party/blink/web_tests/external/wpt/native-io/rename_async_failure_handling.tentative.https.any.js

@@ -4,6 +4,11 @@
 
 'use strict';
 
+setup(async () => {
+  assert_implements(nativeIO.rename,
+                    "nativeIO.rename is not implemented.");
+});
+
 promise_test(async testCase => {
   const file1 = await nativeIO.open('test_file_1');
   const file2 = await nativeIO.open('test_file_2');

third_party/blink/web_tests/external/wpt/native-io/rename_sync_failure_handling.tentative.https.any.js

@@ -4,6 +4,12 @@
 
 'use strict';
 
+setup(() => {
+  // Without this assertion, one test passes even if renameSync is not defined
+  assert_implements(nativeIO.renameSync,
+                    "nativeIO.renameSync is not implemented.");
+});
+
 test(testCase => {
   const file1 = nativeIO.openSync('test_file_1');
   const file2 = nativeIO.openSync('test_file_2');