Guest mode causes certain settings to be hidden.

chrome/browser/ui/webui/options/browser_options_handler.cc

Index: chrome/browser/ui/webui/options/browser_options_handler.cc
diff --git a/chrome/browser/ui/webui/options/browser_options_handler.cc b/chrome/browser/ui/webui/options/browser_options_handler.cc
index 50289d3b1b62d28035859569b14ddf0acfdef3a8..26a8cb215332693c2b96c9f7b308ca56eead860d 100644
--- a/chrome/browser/ui/webui/options/browser_options_handler.cc
+++ b/chrome/browser/ui/webui/options/browser_options_handler.cc
@@ -540,11 +540,6 @@ void BrowserOptionsHandler::GetLocalizedValues(base::DictionaryValue* values) {
   // Pass along sync status early so it will be available during page init.
   values->Set("syncData", GetSyncStateDictionary().release());
 
-  // The Reset Profile Settings feature makes no sense for an off-the-record
-  // profile (e.g. in Guest mode on Chrome OS), so hide it.
-  values->SetBoolean("enableResetProfileSettings",
-                     !Profile::FromWebUI(web_ui())->IsOffTheRecord());
-
   values->SetString("privacyLearnMoreURL", chrome::kPrivacyLearnMoreURL);
   values->SetString("doNotTrackLearnMoreURL", chrome::kDoNotTrackLearnMoreURL);
 
@@ -600,6 +595,9 @@ void BrowserOptionsHandler::GetLocalizedValues(base::DictionaryValue* values) {
   if (ShouldShowMultiProfilesUserList())
     values->Set("profilesInfo", GetProfilesInfoList().release());
 
+  values->SetBoolean("profileIsGuest",
+                     Profile::FromWebUI(web_ui())->IsOffTheRecord());
+
   values->SetBoolean("profileIsSupervised",
                      Profile::FromWebUI(web_ui())->IsSupervised());
 
@@ -844,6 +842,10 @@ void BrowserOptionsHandler::InitializeHandler() {
   }
 #endif
 
+  // No preferences below this point may be modified by guest profiles.
+  if (Profile::FromWebUI(web_ui())->IsGuestSession())
+    return;
+
   auto_open_files_.Init(
       prefs::kDownloadExtensionsToOpen, prefs,
       base::Bind(&BrowserOptionsHandler::SetupAutoOpenFileTypes,