Adds a feature to MHTML serialization that omits subframes and subresources marked no-store.

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 67 matching lines @@
         // return true and populate |rewrittenLink| with a desired value of the
         // html attribute value to be used in place of the original link.
         // (i.e. in place of img.src or iframe.src or object.data).
         //
         // If no link rewriting is desired, this method should return false.
         virtual bool rewriteLink(const Element&, String& rewrittenLink)
         {
             return false;
         }
 
-        // Tells whether to skip serialization of a subresource with a given URI.
-        // Used to deduplicate resources across multiple frames.
-        virtual bool shouldSkipResource(const KURL&)
+        // Tells whether to skip serialization of a subresource or CSSStyleSheet
+        // with a given URI. Used to deduplicate resources across multiple frames.
+        virtual bool shouldSkipResourceWithURL(const KURL&)
         {
             return false;
         }
+
+        // Tells whether to skip serialization of a subresource.
+        virtual bool shouldSkipResource(Resource*)

[Łukasz Anforowicz, 2016/05/18 17:27:25]

nit: I wonder we can avoid introducing a new method and instead change the
signature of the old method (so that it takes Resource* instead of KURL&).  Less
code = simpler and more readable code?

Hmmm... I guess what I am proposing requires some refactoring of
FrameSerializer.cpp to change FrameSerializer::shouldAddURL to something taking
a Resource* instead... if this is too big of a change for the current CL, then
maybe it can be done in a follow-up CL.

Also... I am not sure if what I am proposing would work for shouldAddURL(url)
call in FrameSerializer::serializeCSSStyleSheet (i.e. there is no Resource*
anywhere nearby in this case...).

WDYT?  Just an idea :-)

[dewittj, 2016/05/19 04:13:17]

Only other way that would work is if you had:
shouldSkipResourceWithURL(const KURL&, Resource*) where the Resource could be
nullptr.  It didn't seem very clean, especially since in the implementation
there was never a need for /both/ the URL and the Resource.

So I'd like to leave this as-is, perhaps better names are in order?  I'm open to
suggestions.

[Łukasz Anforowicz, 2016/05/19 17:00:13]

This is fine.  Thanks for looking into this.

[dewittj, 2016/05/19 18:18:35]

Acknowledged.

+        {
+            return false;
+        }
     };
 
     // Constructs a serializer that will write output to the given vector 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(Vector<SerializedResource>&, Delegate&);
 
     // Initiates the serialization of the frame. All serialized content and
     // retrieved resources are added to the Vector passed to the constructor.
@@ skipping 22 matching lines @@
 
     Vector<SerializedResource>* m_resources;
     HashSet<KURL> m_resourceURLs;
 
     Delegate& m_delegate;
 };
 
 } // namespace blink
 
 #endif // FrameSerializer_h