Fix DCHECK failure in page_setup.cc on Linux.

printing/print_settings_initializer_gtk.cc

Index: printing/print_settings_initializer_gtk.cc
diff --git a/printing/print_settings_initializer_gtk.cc b/printing/print_settings_initializer_gtk.cc
index fd7a5fda1b0c3a234b8107ad168376c37d1cc5d2..60ab530a7cdb4a9549c82ef2d87c1c57e6d95620 100644
--- a/printing/print_settings_initializer_gtk.cc
+++ b/printing/print_settings_initializer_gtk.cc
@@ -62,11 +62,15 @@ void PrintSettingsInitializerGtk::InitPrintSettings(
       static_cast<int>(page_height_in_pixel));
     printable_area_device_units.SetRect(
       static_cast<int>(
-          NativeMetafile::kLeftMarginInInch * printing::kPixelsPerInch),
+          NativeMetafile::kLeftMarginInInch * dpi),
       static_cast<int>(
-          NativeMetafile::kTopMarginInInch * printing::kPixelsPerInch),
-      page_width_in_pixel,
-      page_height_in_pixel);
+          NativeMetafile::kTopMarginInInch * dpi),
+      page_width_in_pixel -
+      (NativeMetafile::kLeftMarginInInch +
+       NativeMetafile::kRightMarginInInch) * dpi,
+      page_height_in_pixel -
+      (NativeMetafile::kTopMarginInInch +
+       NativeMetafile::kBottomMarginInInch) * dpi);
   }
 
   print_settings->set_dpi(dpi);