Oilpan: Change Persistent members of Resource subclasses to Member.

Source/core/fetch/DocumentResource.cpp

Index: Source/core/fetch/DocumentResource.cpp
diff --git a/Source/core/fetch/DocumentResource.cpp b/Source/core/fetch/DocumentResource.cpp
index fcb4c5606c9db75b7cef21003f4a1633cb7ad7b3..26b7cdfd66512563fab3814f71a07d3dc583a695 100644
--- a/Source/core/fetch/DocumentResource.cpp
+++ b/Source/core/fetch/DocumentResource.cpp
@@ -42,6 +42,12 @@ DocumentResource::~DocumentResource()
 {
 }
 
+void DocumentResource::trace(Visitor* visitor)
+{
+    visitor->trace(m_document);
+    Resource::trace(visitor);
+}
+
 void DocumentResource::setEncoding(const String& chs)
 {
     m_decoder->setEncoding(chs, TextResourceDecoder::EncodingFromHTTPHeader);