Atomics.wait throws when called on the main thread.

third_party/WebKit/Source/bindings/core/v8/V8PerIsolateData.cpp

 /*
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 37 matching lines @@
 static void beforeCallEnteredCallback(v8::Isolate* isolate) {
   RELEASE_ASSERT(!ScriptForbiddenScope::isScriptForbidden());
 }
 
 static void microtasksCompletedCallback(v8::Isolate* isolate) {
   V8PerIsolateData::from(isolate)->runEndOfScopeTasks();
 }
 
 V8PerIsolateData::V8PerIsolateData(WebTaskRunner* taskRunner)
     : m_isolateHolder(WTF::makeUnique<gin::IsolateHolder>(
-          taskRunner ? taskRunner->toSingleThreadTaskRunner() : nullptr)),
+          taskRunner ? taskRunner->toSingleThreadTaskRunner() : nullptr,
+          gin::IsolateHolder::kSingleThread,
+          isMainThread() ? gin::IsolateHolder::kDisallowAtomicsWait
+                         : gin::IsolateHolder::kAllowAtomicsWait)),
       m_stringCache(WTF::wrapUnique(new StringCache(isolate()))),
       m_hiddenValue(V8HiddenValue::create()),
       m_privateProperty(V8PrivateProperty::create()),
       m_constructorMode(ConstructorMode::CreateNewObject),
       m_useCounterDisabled(false),
       m_isHandlingRecursionLevelError(false),
       m_isReportingException(false) {
   // FIXME: Remove once all v8::Isolate::GetCurrent() calls are gone.
   isolate()->Enter();
   isolate()->AddBeforeCallEnteredCallback(&beforeCallEnteredCallback);
@@ skipping 343 matching lines @@
   ScriptWrappableVisitor* current = currentVisitor();
   if (current)
     current->performCleanup();
 
   V8PerIsolateData::from(m_isolate)->m_scriptWrappableVisitor.swap(
       m_savedVisitor);
   m_isolate->SetEmbedderHeapTracer(currentVisitor());
 }
 
 }  // namespace blink