Factor out gin::IsolateHolder's constructor

third_party/WebKit/Source/core/workers/WorkerBackingThread.cpp

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/workers/WorkerBackingThread.h"
 
 #include "bindings/core/v8/V8Binding.h"
 #include "bindings/core/v8/V8GCController.h"
 #include "bindings/core/v8/V8IdleTaskRunner.h"
 #include "bindings/core/v8/V8Initializer.h"
@@ skipping 43 matching lines @@
                                          bool shouldCallGCOnShutdown)
     : m_backingThread(WebThreadSupportingGC::createForThread(thread)),
       m_isOwningThread(false),
       m_shouldCallGCOnShutdown(shouldCallGCOnShutdown) {}
 
 WorkerBackingThread::~WorkerBackingThread() {}
 
 void WorkerBackingThread::initialize() {
   DCHECK(!m_isolate);
   m_backingThread->initialize();
-  m_isolate = V8PerIsolateData::initialize(
-      m_backingThread->platformThread().getWebTaskRunner());
+  WebTaskRunner* taskRunner =
+      backingThread().platformThread().getWebTaskRunner();
+  m_isolate = V8PerIsolateData::initialize(WTF::makeUnique<gin::IsolateHolder>(
+      taskRunner ? taskRunner->toSingleThreadTaskRunner() : nullptr));
   addWorkerIsolate(m_isolate);
   V8Initializer::initializeWorker(m_isolate);
 
   ThreadState::current()->registerTraceDOMWrappers(
       m_isolate, V8GCController::traceDOMWrappers,
       ScriptWrappableVisitor::invalidateDeadObjectsInMarkingDeque,
       ScriptWrappableVisitor::performCleanup);
   if (RuntimeEnabledFeatures::v8IdleTasksEnabled())
     V8PerIsolateData::enableIdleTasks(
         m_isolate, WTF::wrapUnique(new V8IdleTaskRunner(
@@ skipping 32 matching lines @@
 
 // static
 void WorkerBackingThread::setRAILModeOnWorkerThreadIsolates(
     v8::RAILMode railMode) {
   MutexLocker lock(isolatesMutex());
   for (v8::Isolate* isolate : isolates())
     isolate->SetRAILMode(railMode);
 }
 
 }  // namespace blink