Revert "Worker: Abort all inflight tasks in Worklet::ContextDestroyed()"

This reverts commit c95749d2.

Reason for revert:
Some web_tests are crashing due to this change.
https://test-results.appspot.com/data/layout_results/WebKit_Linux_Trusty_ASAN/26566/webkit_layout_tests/layout-test-results/results.html

Original change's description:
> Worker: Abort all inflight tasks in Worklet::ContextDestroyed()
> 
> Before this CL, all inflight tasks can be retained in
> Worklet::pending_tasks_set_ even after context destruction, and that causes
> dcheck failures in the destructor of Worklet. This CL fixes it by aborting them
> in Worklet::ContextDestroyed().
> 
> In addition, this CL adds test coverage of addModule() calls on a detached
> iframe. In the tests, LayoutWorklet is used for testing main thread worklets
> instead of PaintWorklet because PaintWorklet will be switched to
> off-the-main-thread worklets (see https://crbug.com/829967).
> 
> Bug: 962355
> Change-Id: I7da71e7f4bdcbfa20125853832122a733c118a7a
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1626062
> Reviewed-by: Matt Falkenhagen <falken@chromium.org>
> Commit-Queue: Hiroki Nakagawa <nhiroki@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#662923}

TBR=falken@chromium.org,nhiroki@chromium.org

Change-Id: I54041a299dfdc74ff298b001cd42609fe2c11901
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 962355
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1627843Reviewed-by: Hiroki Nakagawa <nhiroki@chromium.org>
Commit-Queue: Hiroki Nakagawa <nhiroki@chromium.org>
Cr-Commit-Position: refs/heads/master@{#662962}

third_party/blink/renderer/core/workers/worklet.cc

@@ -94,15 +94,6 @@ void Worklet::ContextDestroyed(ExecutionContext* execution_context) {
   module_responses_map_->Dispose();
   for (const auto& proxy : proxies_)
     proxy->TerminateWorkletGlobalScope();
-  for (auto iter = pending_tasks_set_.begin();
-       iter != pending_tasks_set_.end();) {
-    // Move the iterator forward before calling WorkletPendingTasks::Abort()
-    // because that modifies |pending_tasks_set_| and invalidates the iterator.
-    auto current = iter;
-    ++iter;
-    (*current)->Abort();
-  }
-  DCHECK(!HasPendingTasks());
 }
 
 bool Worklet::HasPendingTasks() const {

third_party/blink/web_tests/http/tests/worklet/import-on-detached-iframe.html

@@ -17,53 +17,20 @@ function with_iframe(url) {
     });
 }
 
-// These tests should not be upstreamed to WPT because the spec does not define
+// This test should not be upstreamed to WPT because the spec does not define
 // behavior in the case where addModule() is called from a detached frame.
-
-promise_test(async t => {
-  const frame = await with_iframe('resources/blank.html');
-  const worklet = frame.contentWindow.CSS.layoutWorklet;
-  frame.remove();
-  await promise_rejects(
-      t, 'InvalidStateError',
-      worklet.addModule('resources/empty-worklet-script.js'));
-}, '[main thread worklet] addModule() on a detached iframe should be ' +
-   'rejected.');
-
-promise_test(async t => {
-  const frame = await with_iframe('resources/blank.html');
-  const worklet = frame.contentWindow.CSS.animationWorklet;
-  frame.remove();
-  await promise_rejects(
-      t, 'InvalidStateError',
-      worklet.addModule('resources/empty-worklet-script.js'));
-}, '[off main thread worklet] addModule() on a detached iframe should be ' +
-   'rejected.');
-
-promise_test(async t => {
-  const frame = await with_iframe('resources/blank.html');
-  const worklet = frame.contentWindow.CSS.layoutWorklet;
-  const promise = worklet.addModule('resources/empty-worklet-script.js');
-  frame.remove();
-
-  // Wait a moment to confirm that asynchronous addModule() operation on the
-  // detached iframe doesn't crash. We cannot wait for the promise returned by
-  // addModule() because it's never settled after context destruction.
-  await new Promise(resolve => setTimeout(resolve, 10));
-}, '[main thread worklet] detaching an iframe after addModule() should not ' +
-   'crash.');
-
-promise_test(async t => {
-  const frame = await with_iframe('resources/blank.html');
-  const worklet = frame.contentWindow.CSS.animationWorklet;
-  const promise = worklet.addModule('resources/empty-worklet-script.js');
-  frame.remove();
-
-  // Wait a moment to confirm that asynchronous addModule() operation on the
-  // detached iframe doesn't crash. We cannot wait for the promise returned by
-  // addModule() because it's never settled after context destruction.
-  await new Promise(resolve => setTimeout(resolve, 10));
-}, '[off main thread worklet] detaching an iframe after addModule() should ' +
-   'not crash.');
+promise_test(t => {
+  const kFrameUrl = 'resources/blank.html';
+  const kScriptUrl = 'resources/empty-worklet-script.js';
+
+  return with_iframe(kFrameUrl)
+    .then(frame => {
+        let worklet = frame.contentWindow.CSS.paintWorklet;
+        frame.remove();
+        return worklet.addModule(kScriptUrl);
+      })
+    .then(() => assert_unreached('addModule() should fail.'))
+    .catch(e => assert_equals(e.name, 'InvalidStateError', e));
+}, 'addModule() on a detached iframe should be rejected.');
 
 </script>