The chrome.screenlockPrivate API allows select apps to control the ChromeOS ScreenLocker.

chrome/browser/profiles/chrome_browser_main_extra_parts_profiles.cc

Index: chrome/browser/profiles/chrome_browser_main_extra_parts_profiles.cc
diff --git a/chrome/browser/profiles/chrome_browser_main_extra_parts_profiles.cc b/chrome/browser/profiles/chrome_browser_main_extra_parts_profiles.cc
index 1bcb6944f3600d9a7fc14de1d856e5983084a519..2d7e1447726a55d9e8ea1c97a9d9d7d4df4dd660 100644
--- a/chrome/browser/profiles/chrome_browser_main_extra_parts_profiles.cc
+++ b/chrome/browser/profiles/chrome_browser_main_extra_parts_profiles.cc
@@ -137,6 +137,7 @@
 #if defined(OS_CHROMEOS)
 #include "chrome/browser/chromeos/extensions/input_method_api.h"
 #include "chrome/browser/chromeos/extensions/media_player_api.h"
+#include "chrome/browser/chromeos/extensions/screenlock_private_api.h"
 #include "chrome/browser/extensions/api/input_ime/input_ime_api.h"
 #include "chrome/browser/extensions/api/networking_private/networking_private_event_router_factory.h"
 #if defined(FILE_MANAGER_EXTENSION)
@@ -267,6 +268,7 @@ EnsureBrowserContextKeyedServiceFactoriesBuilt() {
 #if defined(OS_CHROMEOS)
   extensions::InputImeAPI::GetFactoryInstance();
   extensions::InputMethodAPI::GetFactoryInstance();
+  extensions::ScreenlockPrivateEventRouter::GetFactoryInstance();
 #endif
   extensions::LocationManager::GetFactoryInstance();
   extensions::ManagementAPI::GetFactoryInstance();