Oilpan: add temporary plugin ignore exemption for DataRef<T>::RefPtr<T>.

third_party/WebKit/Source/core/style/DataRef.h

Index: third_party/WebKit/Source/core/style/DataRef.h
diff --git a/third_party/WebKit/Source/core/style/DataRef.h b/third_party/WebKit/Source/core/style/DataRef.h
index d1511da140e1d07f1154dcc1f4f00e70852c8145..a03fab56770aabc701d202a03e968b1ebecbb70d 100644
--- a/third_party/WebKit/Source/core/style/DataRef.h
+++ b/third_party/WebKit/Source/core/style/DataRef.h
@@ -24,6 +24,7 @@
 #ifndef DataRef_h
 #define DataRef_h
 
+#include "platform/heap/Handle.h"
 #include "wtf/Allocator.h"
 #include "wtf/RefPtr.h"
 
@@ -66,6 +67,9 @@ public:
 
     void operator=(std::nullptr_t) { m_data = nullptr; }
 private:
+    // TODO(Oilpan): remove this once the GC plugin change in r359074 has
+    // rolled out & been deployed.
+    GC_PLUGIN_IGNORE("553613")
     RefPtr<T> m_data;
 };