Add support for starting an extension print job to print preview

printing/print_job_constants.cc

 // 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.
 
 #include "printing/print_job_constants.h"
 
 namespace printing {
 
 // True if this is the first preview request.
 const char kIsFirstRequest[] = "isFirstRequest";
@@ skipping 142 matching lines @@
 // Additional printer options.
 const char kSettingPrinterOptions[] = "printerOptions";
 
 // Print to PDF option: true if selected, false if not.
 const char kSettingPrintToPDF[] = "printToPDF";
 
 // Print using Privet option: true if destination is a Privet printer, false if
 // not.
 const char kSettingPrintWithPrivet[] = "printWithPrivet";
 
+// Print using extension option: true if destination is an extension printer,
+// false if not.
+const char kSettingPrintWithExtension[] = "printWithExtension";
+
 // Ticket option. Contains the ticket in CJT format.
 const char kSettingTicket[] = "ticket";
 
 // Whether to print CSS backgrounds.
 const char kSettingShouldPrintBackgrounds[] = "shouldPrintBackgrounds";
 
 // Whether to print selection only.
 const char kSettingShouldPrintSelectionOnly[] = "shouldPrintSelectionOnly";
 
 // Whether to print selection only.
@@ skipping 18 matching lines @@
 const char kGreyscale[] = "Greyscale";
 const char kMonochrome[] = "Monochrome";
 const char kNormal[] = "Normal";
 const char kNormalGray[] = "Normal.Gray";
 const char kRGB[] = "RGB";
 const char kRGBA[] = "RGBA";
 const char kRGB16[] = "RGB16";
 #endif
 
 }  // namespace printing