PrintPreview: Added code to honor the grayscale color model.

printing/print_job_constants.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 PRINTING_PRINT_JOB_CONSTANTS_H_
 #define PRINTING_PRINT_JOB_CONSTANTS_H_
 
 #include "printing/printing_export.h"
 
 namespace printing {
@@ skipping 80 matching lines @@
 // Print job color mode values.
 enum ColorModels {
   UNKNOWN_COLOR_MODEL,
   GRAY,
   COLOR,
   CMYK,
   CMY,
   KCMY,
   CMY_K,  // CMY_K represents CMY+K.
   BLACK,
+  GRAYSCALE,
   RGB,
   RGB16,
   RGBA,
   COLORMODE_COLOR,  // Used in samsung printer ppds.
   COLORMODE_MONOCHROME,  // Used in samsung printer ppds.
   HP_COLOR_COLOR, // Used in HP color printer ppds.
   HP_COLOR_BLACK, // Used in HP color printer ppds.
   PRINTOUTMODE_NORMAL,  // Used in foomatic ppds.
   PRINTOUTMODE_NORMAL_GRAY,  // Used in foomatic ppds.
   PROCESSCOLORMODEL_CMYK,  // Used in canon printer ppds.
   PROCESSCOLORMODEL_GREYSCALE,  // Used in canon printer ppds.
   PROCESSCOLORMODEL_RGB,  // Used in canon printer ppds
 };
 
 // What kind of margins to use.
 enum MarginType {
   DEFAULT_MARGINS,  // Default varies depending on headers being enabled or not
   NO_MARGINS,
   CUSTOM_MARGINS,
   PRINTABLE_AREA_MARGINS,
 };
 
 }  // namespace printing
 
 #endif  // PRINTING_PRINT_JOB_CONSTANTS_H_