Auto merge of #17475 - asajeffrey:wpt-workers-exception-handling, r=jdm

Added exception-handling to worker wpt tests.

<!-- Please describe your changes on the following line: -->

Added exception-handling to worker wpt tests.

---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: -->
- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix #15668 and #17460
- [X] These changes do not require tests because these are tests

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tests/wpt/metadata/MANIFEST.json

@@ -615810,7 +615810,7 @@
    "testharness"
   ],
   "workers/Worker_ErrorEvent_error.htm": [
-   "975ca8b575fb2f616623b810696287513b164d2d",
+   "43f1cd277819f57c7708690ff3a91dde8b2a3af5",
    "testharness"
   ],
   "workers/Worker_ErrorEvent_filename.htm": [
@@ -616102,7 +616102,7 @@
    "testharness"
   ],
   "workers/data-url.html": [
-   "50abaf936cfb58ba14e6870c9b7f239f5d54f59c",
+   "a9084f9a3b6fc31d54b564b80869826f132f1166",
    "testharness"
   ],
   "workers/interfaces.idl": [

tests/wpt/metadata/workers/Worker_ErrorEvent_error.htm.ini

@@ -1,2 +0,0 @@
-[Worker_ErrorEvent_error.htm]
-  expected: ERROR

tests/wpt/metadata/workers/data-url.html.ini

@@ -1,6 +1,5 @@
 [data-url.html]
   type: testharness
-  expected: ERROR
   [worker has opaque origin]
     expected: FAIL
 

tests/wpt/web-platform-tests/workers/Worker_ErrorEvent_error.htm

@@ -4,6 +4,10 @@
 <script src=/resources/testharness.js></script>
 <script src=/resources/testharnessreport.js></script>
 <script>
+// The worker events races with the window's load event; if the worker events
+// arrive first, the harness will detect the error event and fail the test.
+setup({ allow_uncaught_exception: true });
+
 var t1 = async_test("Error handler outside the worker should not see the error value");
 var t2 = async_test("Error handlers inside a worker should see the error value");
 

tests/wpt/web-platform-tests/workers/data-url.html

@@ -25,7 +25,9 @@ function assert_worker_construction_fails(test_desc, mime_type, worker_code) {
     w.onmessage = t.step_func_done(function(e) {
       assert_unreached('Should not receive any message back.');
     });
-    w.onerror = t.step_func_done(function() {
+    w.onerror = t.step_func_done(function(e) {
+      // Stop the error from being propagated to the WPT test harness
+      e.preventDefault();
     });
   }, test_desc);
 }