Replace FOR_EACH_OBSERVER in c/b/chromeos with range-based for

chrome/browser/chromeos/system/system_clock.cc

Index: chrome/browser/chromeos/system/system_clock.cc
diff --git a/chrome/browser/chromeos/system/system_clock.cc b/chrome/browser/chromeos/system/system_clock.cc
index 3264e37c6f20d84fd9b3f966f48bd7ce315ad30a..2a300bd503fa9a3c28907288a608f6df463b96ad 100644
--- a/chrome/browser/chromeos/system/system_clock.cc
+++ b/chrome/browser/chromeos/system/system_clock.cc
@@ -212,8 +212,8 @@ void SystemClock::UpdateClockType() {
   // a local owner.
   if (user_manager::UserManager::Get()->IsCurrentUserOwner())
     SetShouldUse24HourClock(ShouldUse24HourClock());
-  FOR_EACH_OBSERVER(SystemClockObserver, observer_list_,
-                    OnSystemClockChanged(this));
+  for (auto& observer : observer_list_)
+    observer.OnSystemClockChanged(this);
 }
 
 }  // namespace system