Oilpan: move MessageChannel to the heap.

Source/core/workers/SharedWorker.cpp

Index: Source/core/workers/SharedWorker.cpp
diff --git a/Source/core/workers/SharedWorker.cpp b/Source/core/workers/SharedWorker.cpp
index 7c73fa66bbcd636520ad6492a19581263e402a51..dd75c77a7c6b2d37eb130b3e563efc748759d5e2 100644
--- a/Source/core/workers/SharedWorker.cpp
+++ b/Source/core/workers/SharedWorker.cpp
@@ -63,7 +63,7 @@ PassRefPtrWillBeRawPtr<SharedWorker> SharedWorker::create(ExecutionContext* cont
 
     RefPtrWillBeRawPtr<SharedWorker> worker = adoptRefWillBeRefCountedGarbageCollected(new SharedWorker(context));
 
-    RefPtr<MessageChannel> channel = MessageChannel::create(context);
+    RefPtrWillBeRawPtr<MessageChannel> channel = MessageChannel::create(context);
     worker->m_port = channel->port1();
     OwnPtr<blink::WebMessagePortChannel> remotePort = channel->port2()->disentangle();
     ASSERT(remotePort);