Add glue for supporting custom MIME types in DataTransfer.

ui/base/clipboard/clipboard.h

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef UI_BASE_CLIPBOARD_CLIPBOARD_H_
 #define UI_BASE_CLIPBOARD_CLIPBOARD_H_
 #pragma once
 
 #include <map>
 #include <string>
@@ skipping 138 matching lines @@
   // Reads HTML from the clipboard, if available. If the HTML fragment requires
   // context to parse, |fragment_start| and |fragment_end| are indexes into
   // markup indicating the beginning and end of the actual fragment. Otherwise,
   // they will contain 0 and markup->size().
   void ReadHTML(Buffer buffer, string16* markup, std::string* src_url,
                 uint32* fragment_start, uint32* fragment_end) const;
 
   // Reads an image from the clipboard, if available.
   SkBitmap ReadImage(Buffer buffer) const;
 
+  void ReadCustomData(Buffer buffer, const string16& type,
+                      string16* data) const;
+
   // Reads a bookmark from the clipboard, if available.
   void ReadBookmark(string16* title, std::string* url) const;
 
   // Reads a file or group of files from the clipboard, if available, into the
   // out parameter.
   void ReadFile(FilePath* file) const;
   void ReadFiles(std::vector<FilePath>* files) const;
 
   // Reads raw data from the clipboard with the given format type. Stores result
   // as a byte vector.
@@ skipping 111 matching lines @@
   static const char kMimeTypeText[];
   static const char kMimeTypeHTML[];
   static const char kMimeTypePNG[];
 
   DISALLOW_COPY_AND_ASSIGN(Clipboard);
 };
 
 }  // namespace ui
 
 #endif  // UI_BASE_CLIPBOARD_CLIPBOARD_H_