When printing a PDF, query and use the print scaling disabled option.

printing/print_job_constants.cc

 // 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.
 
 #include "printing/print_job_constants.h"
 
 namespace printing {
 
 // True if this is the first preview request.
 const char kIsFirstRequest[] = "isFirstRequest";
@@ skipping 93 matching lines @@
 
 // A page range.
 const char kSettingPageRange[] = "pageRange";
 
 // The first page of a page range. (1-based)
 const char kSettingPageRangeFrom[] = "from";
 
 // The last page of a page range. (1-based)
 const char kSettingPageRangeTo[] = "to";
 
+const char kSettingPreviewModifiable[] = "previewModifiable";
+
 // Printer name.
 const char kSettingPrinterName[] = "printerName";
 
 // Print to PDF option: true if selected, false if not.
 const char kSettingPrintToPDF[] = "printToPDF";
 
 // Indices used to represent first preview page and complete preview document.
 const int FIRST_PAGE_INDEX = 0;
 const int COMPLETE_PREVIEW_DOCUMENT_INDEX = -1;
 
 #if defined (USE_CUPS)
 const char kBlack[] = "Black";
 const char kCMYK[] = "CMYK";
 const char kKCMY[] = "KCMY";
 const char kCMY_K[] = "CMY+K";
 const char kCMY[] = "CMY";
 const char kColor[] = "Color";
 const char kGray[] = "Gray";
 const char kGrayscale[] = "Grayscale";
 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