Revert of Remove the concept of a cleanup task

Source/platform/WebThreadSupportingGC.h

Index: Source/platform/WebThreadSupportingGC.h
diff --git a/Source/platform/WebThreadSupportingGC.h b/Source/platform/WebThreadSupportingGC.h
index 01d7212a99c678caadf09570234335c4e2219e36..f25dbc070935f19d6abe6be8bfcdadbc945e5400 100644
--- a/Source/platform/WebThreadSupportingGC.h
+++ b/Source/platform/WebThreadSupportingGC.h
@@ -16,9 +16,9 @@
 namespace blink {
 
 // WebThreadSupportingGC wraps a WebThread and adds support for attaching
-// to and detaching from the Blink GC infrastructure. The initialize method
+// to and detaching from the Blink GC infrastructure. The attachGC method
 // must be called during initialization on the WebThread and before the
-// thread allocates any objects managed by the Blink GC. The shutdown
+// thread allocates any objects managed by the Blink GC. The detach GC
 // method must be called on the WebThread during shutdown when the thread
 // no longer needs to access objects managed by the Blink GC.
 class PLATFORM_EXPORT WebThreadSupportingGC final {
@@ -52,8 +52,8 @@
         m_thread->removeTaskObserver(observer);
     }
 
-    void initialize();
-    void shutdown();
+    void attachGC();
+    void detachGC();
 
     WebThread& platformThread() const
     {