For no margins, or printable area margins, don't factor in the header/footer size.

printing/print_settings.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_settings.h"
 
 #include "base/atomic_sequence_num.h"
 #include "base/logging.h"
 #include "printing/print_job_constants.h"
 #include "printing/units.h"
@@ skipping 140 matching lines @@
   if (display_header_footer) {
     // Hard-code text_height = 0.5cm = ~1/5 of inch.
     header_footer_text_height = ConvertUnit(kSettingHeaderFooterInterstice,
                                             kPointsPerInch, units_per_inch);
   }
   page_setup_device_units_.Init(physical_size_device_units,
                                 printable_area_device_units,
                                 header_footer_text_height);
 
   PageMargins margins;
-  margins.header = header_footer_text_height;
-  margins.footer = header_footer_text_height;
   switch (margin_type) {
     case DEFAULT_MARGINS: {
       // Default margins 1.0cm = ~2/5 of an inch.
       int margin_printer_units = ConvertUnit(1000, kHundrethsMMPerInch,
                                              units_per_inch);
+      margins.header = header_footer_text_height;
+      margins.footer = header_footer_text_height;
       margins.top = margin_printer_units;
       margins.bottom = margin_printer_units;
       margins.left = margin_printer_units;
       margins.right = margin_printer_units;
       break;
     }
     case NO_MARGINS:
     case PRINTABLE_AREA_MARGINS: {
+      margins.header = 0;
+      margins.footer = 0;
       margins.top = 0;
       margins.bottom = 0;
       margins.left = 0;
       margins.right = 0;
       break;
     }
     case CUSTOM_MARGINS: {
+      margins.header = 0;
+      margins.footer = 0;
       margins.top = ConvertUnitDouble(custom_margins_in_points_.top,
                                       printing::kPointsPerInch,
                                       units_per_inch);
       margins.bottom = ConvertUnitDouble(custom_margins_in_points_.bottom,
                                          printing::kPointsPerInch,
                                          units_per_inch);
       margins.left = ConvertUnitDouble(custom_margins_in_points_.left,
                                        printing::kPointsPerInch,
                                        units_per_inch);
       margins.right = ConvertUnitDouble(custom_margins_in_points_.right,
@@ skipping 37 matching lines @@
 }
 
 void PrintSettings::SetOrientation(bool landscape) {
   if (landscape_ != landscape) {
     landscape_ = landscape;
     page_setup_device_units_.FlipOrientation();
   }
 }
 
 }  // namespace printing