Support serializing shadow DOM to MHTML

third_party/WebKit/Source/core/frame/FrameSerializer.h

 /*
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 89 matching lines @@
     // Tells whether to skip serialization of a subresource.
     virtual bool ShouldSkipResource(ResourceHasCacheControlNoStoreHeader) {
       return false;
     }
 
     // Returns custom attributes that need to add in order to serialize the
     // element.
     virtual Vector<Attribute> GetCustomAttributes(const Element&) {
       return Vector<Attribute>();
     }
+
+    // Returns the root of auxiliary DOM tree, i.e. shadow tree, if it needs to
+    // be serialized. The additional element to enclose the serialized
+    // auxiliary DOM tree may be returned.
+    virtual Node* GetAuxiliaryDOMTree(const Element&, Element**) const {
+      return nullptr;
+    }
   };
 
   // Constructs a serializer that will write output to the given deque of
   // SerializedResources and uses the Delegate for controlling some
   // serialization aspects.  Callers need to ensure that both arguments stay
   // alive until the FrameSerializer gets destroyed.
   FrameSerializer(Deque<SerializedResource>&, Delegate&);
 
   // Initiates the serialization of the frame. All serialized content and
   // retrieved resources are added to the Deque passed to the constructor.
@@ skipping 29 matching lines @@
   HashSet<KURL> resource_urls_;
 
   bool is_serializing_css_;
 
   Delegate& delegate_;
 };
 
 }  // namespace blink
 
 #endif  // FrameSerializer_h