Add BackgroundModeOptimizer that can restart the browser

chrome/browser/lifetime/keep_alive_registry.cc

Index: chrome/browser/lifetime/keep_alive_registry.cc
diff --git a/chrome/browser/lifetime/keep_alive_registry.cc b/chrome/browser/lifetime/keep_alive_registry.cc
index f1ed172b2c92f9140e40bc6ce28864e7dfe12da1..77c3ae3b4aaf2a337945b862a264977e709909b3 100644
--- a/chrome/browser/lifetime/keep_alive_registry.cc
+++ b/chrome/browser/lifetime/keep_alive_registry.cc
@@ -92,12 +92,14 @@ void KeepAliveRegistry::Unregister(KeepAliveOrigin origin,
   bool new_keeping_alive = IsKeepingAlive();
   bool new_restart_allowed = IsRestartAllowed();
 
-  if (new_restart_allowed != old_restart_allowed)
-    OnRestartAllowedChanged(new_restart_allowed);
-
+  // Update the KeepAlive state first, so that listeners can check if we are
+  // trying to shutdown.
   if (new_keeping_alive != old_keeping_alive)
     OnKeepAliveStateChanged(new_keeping_alive);
 
+  if (new_restart_allowed != old_restart_allowed)
+    OnRestartAllowedChanged(new_restart_allowed);
+
   DVLOG(1) << "New state of the KeepAliveRegistry:" << *this;
 }