Refactor bookmark clipboard code to be cross platform.

base/scoped_clipboard_writer.h

Index: base/scoped_clipboard_writer.h
===================================================================
--- base/scoped_clipboard_writer.h	(revision 22359)
+++ base/scoped_clipboard_writer.h	(working copy)
@@ -17,6 +17,8 @@
 #include "base/file_path.h"
 #include "base/string16.h"
 
+class Pickle;
+
 // This class is a wrapper for |Clipboard| that handles packing data
 // into a Clipboard::ObjectMap.
 // NB: You should probably NOT be using this class if you include
@@ -55,6 +57,9 @@
   // Pixel format is assumed to be 32-bit BI_RGB.
   void WriteBitmapFromPixels(const void* pixels, const gfx::Size& size);
 
+  // Adds arbitrary data to clipboard.
+  void WritePickledData(const Pickle& pickle, Clipboard::FormatType format);
+
  protected:
   // We accumulate the data passed to the various targets in the |objects_|
   // vector, and pass it to Clipboard::WriteObjects() during object destruction.