Persist offline page info in a navigation entry if needed

content/public/browser/navigation_entry.h

Index: content/public/browser/navigation_entry.h
diff --git a/content/public/browser/navigation_entry.h b/content/public/browser/navigation_entry.h
index 87c17cd29e18c2dd566e6435cc46dbb6716c75d5..1f5a482decd0bae544401027ed720c3bd3d1580a 100644
--- a/content/public/browser/navigation_entry.h
+++ b/content/public/browser/navigation_entry.h
@@ -225,6 +225,9 @@ class NavigationEntry {
 
   // True if this entry is restored and hasn't been loaded.
   virtual bool IsRestored() const = 0;
+
+  // Returns the extra headers (separated by \n) to send during the request.
+  virtual std::string GetExtraHeaders() const = 0;
 };
 
 }  // namespace content