Change the ChromiumPasteboard to have a notion of an alternate clipboard...

webkit/api/public/WebClipboard.h

 /*
  * Copyright (C) 2009 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 28 matching lines @@
     class WebURL;
 
     class WebClipboard {
     public:
         enum Format {
             FormatHTML,
             FormatBookmark,
             FormatSmartPaste
         };
 
-        virtual bool isFormatAvailable(Format) = 0;
+        enum Buffer {
+            BufferStandard,
+            // Used on platforms like the X Window System that treat selection
+            // as a type of clipboard.
+            BufferSelection
+        };
 
-        virtual WebString readPlainText() = 0;
-        virtual WebString readHTML(WebURL*) = 0;
+        virtual bool isFormatAvailable(Format, Buffer) = 0;
+
+        virtual WebString readPlainText(Buffer) = 0;
+        virtual WebString readHTML(Buffer, WebURL*) = 0;
 
         virtual void writeHTML(
             const WebString& htmlText, const WebURL&,
             const WebString& plainText, bool writeSmartPaste) = 0;
         virtual void writeURL(
             const WebURL&, const WebString& title) = 0;
         virtual void writeImage(
             const WebImage&, const WebURL&, const WebString& title) = 0;
 
     protected:
         ~WebClipboard() {}
     };
 
 } // namespace WebKit
 
 #endif