Implement asynchronous interface/plumbing for GetDefaultPrintSettings.

ppapi/api/dev/ppp_printing_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.
  */
 
 /**
  * Definition of the PPP_Printing interface.
  */
 
 // Note: This version should always match the PPB_Printing_Dev interface.
 label Chrome {
-  M21 = 0.6
+  M23 = 0.7
 };
 
 /**
  * Specifies a contiguous range of page numbers to be printed.
  * The page numbers use a zero-based index.
  */
 [assert_size(8)]
 struct PP_PrintPageNumberRange_Dev {
   uint32_t first_page_number;
   uint32_t last_page_number;
@@ skipping 28 matching lines @@
 
   /** Ends the print session. Further calls to PrintPages will fail. */
   void End([in] PP_Instance instance);
 
   /**
    *  Returns true if the current content should be printed into the full page
    *  and not scaled down to fit within the printer's printable area.
    */
   PP_Bool IsScalingDisabled([in] PP_Instance instance);
 };