Add support for generating thunk source from IDL.

ppapi/api/dev/ppb_console_dev.idl

 /* Copyright (c) 2012 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.
  */
 
 /**
  * This file defines the <code>PPB_Console_Dev</code> interface.
  */
 
+[generate_thunk]
+
 label Chrome {
   M14 = 0.1
 };
 
 [assert_size(4)]
 enum PP_LogLevel_Dev {
   PP_LOGLEVEL_TIP = 0,
   PP_LOGLEVEL_LOG = 1,
   PP_LOGLEVEL_WARNING = 2,
   PP_LOGLEVEL_ERROR = 3
@@ skipping 20 matching lines @@
    * wish to override this. For example, if your plugin is a Python
    * interpreter, you would want log messages to contain the source .py file
    * doing the log statement rather than have "python" show up in the console.
    */
   void LogWithSource(
       [in] PP_Instance instance,
       [in] PP_LogLevel_Dev level,
       [in] PP_Var source,
       [in] PP_Var value);
 };