Introduce WorkerThread::willShutdown()

Source/modules/compositorworker/CompositorWorkerManagerTest.cpp

Index: Source/modules/compositorworker/CompositorWorkerManagerTest.cpp
diff --git a/Source/modules/compositorworker/CompositorWorkerManagerTest.cpp b/Source/modules/compositorworker/CompositorWorkerManagerTest.cpp
index 76ad7dbd774b7296c4ea41b087b16ac1bc75388e..ffa4d835118369270e782ab1ba837fbb7cb3f2bb 100644
--- a/Source/modules/compositorworker/CompositorWorkerManagerTest.cpp
+++ b/Source/modules/compositorworker/CompositorWorkerManagerTest.cpp
@@ -51,11 +51,11 @@ private:
         if (m_v8TerminationCallback)
             (*m_v8TerminationCallback)();
     }
-    void willDestroyIsolate() override
+    void willShutdown() override
     {
         v8::Isolate::GetCurrent()->RequestGarbageCollectionForTesting(v8::Isolate::kFullGarbageCollection);
         Heap::collectAllGarbage();
-        CompositorWorkerThread::willDestroyIsolate();
+        CompositorWorkerThread::willShutdown();
     }
 
     WebWaitableEvent* m_startEvent;