Don't expose DocumentWriter to embedding layer

Source/core/fetch/Resource.h

Index: Source/core/fetch/Resource.h
diff --git a/Source/core/fetch/Resource.h b/Source/core/fetch/Resource.h
index 7a3c32dbb627021019ef4b626584e0ed02be5e9c..bbd7d4c37997b5dedeba2ef0af9b35cfc75625e0 100644
--- a/Source/core/fetch/Resource.h
+++ b/Source/core/fetch/Resource.h
@@ -97,6 +97,8 @@ public:
     virtual void appendData(const char*, int);
     virtual void error(Resource::Status);
 
+    void setNeedsSynchronousCacheHit(bool needsSynchronousCacheHit) { m_needsSynchronousCacheHit = needsSynchronousCacheHit; }
+
     void setResourceError(const ResourceError& error) { m_error = error; }
     const ResourceError& resourceError() const { return m_error; }
 
@@ -361,6 +363,8 @@ private:
     unsigned m_type : 4; // Type
     unsigned m_status : 3; // Status
 
+    bool m_needsSynchronousCacheHit : 1;
+
 #ifndef NDEBUG
     bool m_deleted;
     unsigned m_lruIndex;