Always call StorageMonitor::RemoveObserver in ~MediaFileSystemRegistry.

chrome/browser/media_galleries/media_galleries_permission_controller.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/media_galleries/media_galleries_permission_controller.h"
 
 #include "base/base_paths.h"
+#include "base/logging.h"
 #include "base/path_service.h"
 #include "base/stl_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/extensions/api/file_system/file_system_api.h"
 #include "chrome/browser/media_galleries/media_file_system_registry.h"
 #include "chrome/browser/media_galleries/media_galleries_histograms.h"
 #include "chrome/browser/media_galleries/media_gallery_context_menu.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/ui/chrome_select_file_policy.h"
@@ skipping 56 matching lines @@
                  base::Unretained(this)));
 
   // Unretained is safe because |this| owns |context_menu_|.
   context_menu_.reset(
       new MediaGalleryContextMenu(
           base::Bind(&MediaGalleriesPermissionController::DidForgetEntry,
                      base::Unretained(this))));
 }
 
 void MediaGalleriesPermissionController::OnPreferencesInitialized() {
-  if (StorageMonitor::GetInstance())
-    StorageMonitor::GetInstance()->AddObserver(this);
+  DCHECK(StorageMonitor::GetInstance());
+  StorageMonitor::GetInstance()->AddObserver(this);
 
   // |preferences_| may be NULL in tests.
   if (preferences_) {
     preferences_->AddGalleryChangeObserver(this);
     InitializePermissions();
   }
 
   dialog_.reset(create_dialog_callback_.Run(this));
 }
 
 MediaGalleriesPermissionController::MediaGalleriesPermissionController(
     const extensions::Extension& extension,
     MediaGalleriesPreferences* preferences,
     const CreateDialogCallback& create_dialog_callback,
     const base::Closure& on_finish)
     : web_contents_(NULL),
       extension_(&extension),
       on_finish_(on_finish),
       preferences_(preferences),
       create_dialog_callback_(create_dialog_callback) {
   OnPreferencesInitialized();
 }
 
 MediaGalleriesPermissionController::~MediaGalleriesPermissionController() {
-  if (StorageMonitor::GetInstance())
-    StorageMonitor::GetInstance()->RemoveObserver(this);
+  DCHECK(StorageMonitor::GetInstance());
+  StorageMonitor::GetInstance()->RemoveObserver(this);
 
   // |preferences_| may be NULL in tests.
   if (preferences_)
     preferences_->RemoveGalleryChangeObserver(this);
 
   if (select_folder_dialog_.get())
     select_folder_dialog_->ListenerDestroyed();
 }
 
 base::string16 MediaGalleriesPermissionController::GetHeader() const {
@@ skipping 417 matching lines @@
 MediaGalleryPrefId
 MediaGalleriesPermissionController::DialogIdMap::GetPrefId(
     GalleryDialogId id) const {
   DCHECK_LT(id, next_dialog_id_);
   return forward_mapping_[id];
 }
 
 // MediaGalleries dialog -------------------------------------------------------
 
 MediaGalleriesDialog::~MediaGalleriesDialog() {}