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 3efe1c74528e8fbd5e3cb7f5aa76eec24a5cab20..37fdf21180d5d7aa8b8261b011aa1baec1324232 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; }
 
@@ -363,6 +365,8 @@ private:
 
     unsigned m_wasPurged : 1;
 
+    unsigned m_needsSynchronousCacheHit : 1;
+
 #ifndef NDEBUG
     bool m_deleted;
     unsigned m_lruIndex;