Set color model differently for CUPS IPP on macOS

Unlike other printer settings, color does not have its own function in
the Core Printing API [1]. Therefore, color needs to be set using the
generic PMPrintSettingsSetValue() function. When printing using CUPS
IPP, the passed key-value pair must be IPP constants.

All other printer settings work fine with CUPS IPP because they are
handled with their own Core Printing functions.

[1] https://developer.apple.com/documentation/applicationservices/core_printing

Bug: 1106437
Change-Id: I7ad153fc97f9e5797b263a6ec2ac10726deb27b6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2303992
Commit-Queue: Daniel Hosseinian <dhoss@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Cr-Commit-Position: refs/heads/master@{#789726}

printing/printing_context_mac.mm

@@ -6,6 +6,7 @@
 
 #import <AppKit/AppKit.h>
 #import <QuartzCore/QuartzCore.h>
+#include <cups/cups.h>
 
 #import <iomanip>
 #import <numeric>
@@ -16,6 +17,7 @@
 #include "base/strings/utf_string_conversions.h"
 #include "base/values.h"
 #include "printing/print_settings_initializer_mac.h"
+#include "printing/printing_features.h"
 #include "printing/units.h"
 
 namespace printing {
@@ -389,7 +391,12 @@ bool PrintingContextMac::SetOutputColor(int color_mode) {
       static_cast<PMPrintSettings>([print_info_.get() PMPrintSettings]);
   std::string color_setting_name;
   std::string color_value;
-  GetColorModelForMode(color_mode, &color_setting_name, &color_value);
+  if (base::FeatureList::IsEnabled(features::kCupsIppPrintingBackend)) {
+    color_setting_name = CUPS_PRINT_COLOR_MODE;
+    color_value = GetIppColorModelForMode(color_mode);
+  } else {
+    GetColorModelForMode(color_mode, &color_setting_name, &color_value);
+  }
   base::ScopedCFTypeRef<CFStringRef> color_setting(
       base::SysUTF8ToCFStringRef(color_setting_name));
   base::ScopedCFTypeRef<CFStringRef> output_color(