MD Site Settings: Implement the third-party checkbox for Cookies.

chrome/browser/extensions/api/settings_private/prefs_util.cc

Index: chrome/browser/extensions/api/settings_private/prefs_util.cc
diff --git a/chrome/browser/extensions/api/settings_private/prefs_util.cc b/chrome/browser/extensions/api/settings_private/prefs_util.cc
index 0a573c0da6162f11d0612f3cea1a4e43364c53e3..7ae64a898d4ff38807703982f52e1cd57ce996ce 100644
--- a/chrome/browser/extensions/api/settings_private/prefs_util.cc
+++ b/chrome/browser/extensions/api/settings_private/prefs_util.cc
@@ -130,6 +130,10 @@ const PrefsUtil::TypedPrefMap& PrefsUtil::GetWhitelistedKeys() {
   (*s_whitelist)["translate_blocked_languages"] =
       settings_private::PrefType::PREF_TYPE_LIST;
 
+  // Site Settings prefs.
+  (*s_whitelist)["profile.block_third_party_cookies"] =
+      settings_private::PrefType::PREF_TYPE_BOOLEAN;
+
   // Clear browsing data settings.
   (*s_whitelist)["browser.clear_data.browsing_history"] =
       settings_private::PrefType::PREF_TYPE_BOOLEAN;