Simplify LoginState methods.

chrome/browser/chromeos/settings/system_settings_provider.cc

Index: chrome/browser/chromeos/settings/system_settings_provider.cc
diff --git a/chrome/browser/chromeos/settings/system_settings_provider.cc b/chrome/browser/chromeos/settings/system_settings_provider.cc
index 495f7d8ff38a0360f96f3d260f84fc37a2a0fee5..496b2117eca79887784b7de1b616851e3cc9f5f7 100644
--- a/chrome/browser/chromeos/settings/system_settings_provider.cc
+++ b/chrome/browser/chromeos/settings/system_settings_provider.cc
@@ -29,9 +29,11 @@ SystemSettingsProvider::~SystemSettingsProvider() {
 
 void SystemSettingsProvider::DoSet(const std::string& path,
                                    const base::Value& in_value) {
-  // Non-guest users can change the time zone.
-  if (LoginState::Get()->IsGuestUser())
+  // Only non-guest users can change the time zone.
+  if (LoginState::Get()->IsGuestSessionUser() ||
+      LoginState::Get()->IsPublicSessionUser()) {
     return;
+  }
 
   if (path == kSystemTimezone) {
     base::string16 timezone_id;