Implement WebThreadSupportingGC, which wraps a WebThread attached to Oilpan's GC

Source/core/workers/WorkerThread.h

Index: Source/core/workers/WorkerThread.h
diff --git a/Source/core/workers/WorkerThread.h b/Source/core/workers/WorkerThread.h
index 80a2bf549d83d441c9a8c73508a7b5a837fc746b..42856aec26795ac0427d7b95fc3bd1d86cfdfdbb 100644
--- a/Source/core/workers/WorkerThread.h
+++ b/Source/core/workers/WorkerThread.h
@@ -31,10 +31,8 @@
 #include "core/frame/csp/ContentSecurityPolicy.h"
 #include "core/workers/WorkerGlobalScope.h"
 #include "platform/SharedTimer.h"
-#include "platform/heap/glue/MessageLoopInterruptor.h"
-#include "platform/heap/glue/PendingGCRunner.h"
+#include "platform/WebThreadSupportingGC.h"
 #include "platform/weborigin/SecurityOrigin.h"
-#include "public/platform/WebThread.h"
 #include "wtf/Forward.h"
 #include "wtf/MessageQueue.h"
 #include "wtf/OwnPtr.h"
@@ -115,9 +113,7 @@ namespace blink {
         bool m_terminated;
         OwnPtr<WorkerSharedTimer> m_sharedTimer;
         MessageQueue<WorkerThreadTask> m_debuggerMessageQueue;
-        OwnPtr<PendingGCRunner> m_pendingGCRunner;
         OwnPtr<WebThread::TaskObserver> m_microtaskRunner;
-        OwnPtr<MessageLoopInterruptor> m_messageLoopInterruptor;
 
         WorkerLoaderProxy& m_workerLoaderProxy;
         WorkerReportingProxy& m_workerReportingProxy;
@@ -132,12 +128,12 @@ namespace blink {
         // Used to signal thread shutdown.
         OwnPtr<blink::WebWaitableEvent> m_shutdownEvent;
 
-        // FIXME: This has to be last because of crbug.com/401397 - the
-        // WorkerThread might get deleted before it had a chance to properly
+        // FIXME: This has to be last because of crbug.com/401397.
+        // A WorkerThread might get deleted before it had a chance to properly
         // shut down. By deleting the WebThread first, we can guarantee that
         // no pending tasks on the thread might want to access any of the other
         // members during the WorkerThread's destruction.
-        OwnPtr<blink::WebThread> m_thread;
+        OwnPtr<WebThreadSupportingGC> m_thread;
     };
 
 } // namespace blink