CameraPresenceNotifier observers removal supported.

chrome/browser/ui/webui/chromeos/login/user_image_screen_handler.cc

 // Copyright (c) 2013 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/ui/webui/chromeos/login/user_image_screen_handler.h"
 
 #include "ash/audio/sounds.h"
 #include "base/command_line.h"
 #include "base/logging.h"
 #include "base/metrics/histogram.h"
@@ skipping 30 matching lines @@
   ui::ResourceBundle& bundle = ui::ResourceBundle::GetSharedInstance();
   media::SoundsManager* manager = media::SoundsManager::Get();
   manager->Initialize(SOUND_OBJECT_DELETE,
                       bundle.GetRawDataResource(IDR_SOUND_OBJECT_DELETE_WAV));
   manager->Initialize(SOUND_CAMERA_SNAP,
                       bundle.GetRawDataResource(IDR_SOUND_CAMERA_SNAP_WAV));
 }
 
 UserImageScreenHandler::~UserImageScreenHandler() {
   if (screen_) {
-    CameraPresenceNotifier::GetInstance()->RemoveObserver(screen_);

[ygorshenin1, 2014/04/03 11:45:49]

Please, leave the call to RemoveObserver().

     screen_->OnActorDestroyed(this);
   }
 }
 
 void UserImageScreenHandler::Initialize() {
   if (show_on_init_) {
     Show();
     show_on_init_ = false;
   }
 }
@@ skipping 13 matching lines @@
 
   // When shown, query camera presence.
   if (!screen_)
     return;
   CameraPresenceNotifier::GetInstance()->AddObserver(screen_);
   if (is_ready_)
     screen_->OnScreenReady();
 }
 
 void UserImageScreenHandler::Hide() {
-  CameraPresenceNotifier::GetInstance()->RemoveObserver(screen_);
+  if (screen_)

[ygorshenin1, 2014/04/03 11:45:49]

It's OK to remove NULL from observer list.

+    CameraPresenceNotifier::GetInstance()->RemoveObserver(screen_);
 }
 
 void UserImageScreenHandler::PrepareToShow() {
 }
 
 void UserImageScreenHandler::DeclareLocalizedValues(
     LocalizedValuesBuilder* builder) {
   builder->Add("userImageScreenTitle", IDS_USER_IMAGE_SCREEN_TITLE);
   builder->Add("userImageScreenDescription",
                IDS_OPTIONS_CHANGE_PICTURE_DIALOG_TEXT);
@@ skipping 122 matching lines @@
 
 void UserImageScreenHandler::HideCurtain() {
   CallJS("hideCurtain");
 }
 
 void UserImageScreenHandler::SetProfilePictureEnabled(bool enabled) {
   CallJS("setProfilePictureEnabled", enabled);
 }
 
 }  // namespace chromeos