Oilpan: handle WorkerObjectProxy::m_executionContext ref better.

third_party/WebKit/Source/core/workers/WorkerObjectProxy.h

Index: third_party/WebKit/Source/core/workers/WorkerObjectProxy.h
diff --git a/third_party/WebKit/Source/core/workers/WorkerObjectProxy.h b/third_party/WebKit/Source/core/workers/WorkerObjectProxy.h
index 397d0b2471f80a1160170107d61bedecc93f2292..b4e81f2a7429d48496713705627ecf921bf1e263 100644
--- a/third_party/WebKit/Source/core/workers/WorkerObjectProxy.h
+++ b/third_party/WebKit/Source/core/workers/WorkerObjectProxy.h
@@ -34,6 +34,7 @@
 #include "core/CoreExport.h"
 #include "core/dom/MessagePort.h"
 #include "core/workers/WorkerReportingProxy.h"
+#include "platform/heap/Handle.h"
 #include "wtf/PassOwnPtr.h"
 #include "wtf/PassRefPtr.h"
 
@@ -78,6 +79,7 @@ protected:
 
 private:
     // These objects always outlive this proxy.
+    GC_PLUGIN_IGNORE("553613")
     ExecutionContext* m_executionContext;
     WorkerMessagingProxy* m_messagingProxy;
 };