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

chrome/browser/chromeos/camera_presence_notifier.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/chromeos/camera_presence_notifier.h"
 
 #include "base/bind.h"
 #include "base/memory/singleton.h"
 #include "base/time/time.h"
 #include "chrome/browser/chromeos/camera_detector.h"
@@ skipping 46 matching lines @@
   CameraDetector::StartPresenceCheck(
       base::Bind(&CameraPresenceNotifier::OnCameraPresenceCheckDone,
                  weak_factory_.GetWeakPtr()));
 }
 
 void CameraPresenceNotifier::OnCameraPresenceCheckDone() {
   bool is_camera_present =
       CameraDetector::camera_presence() == CameraDetector::kCameraPresent;
   if (is_camera_present != camera_present_on_last_check_) {
     camera_present_on_last_check_ = is_camera_present;
-    FOR_EACH_OBSERVER(Observer,
-                      observers_,
-                      OnCameraPresenceCheckDone(camera_present_on_last_check_));
+    for (auto& observer : observers_)
+      observer.OnCameraPresenceCheckDone(camera_present_on_last_check_);
   }
 }
 
 }  // namespace chromeos