Always call StorageMonitor::RemoveObserver in ~MediaFileSystemRegistry.

chrome/browser/media_galleries/media_file_system_registry.cc

 // Copyright (c) 2012 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_file_system_registry.h"
 
 #include <stddef.h>
 
 #include <set>
 #include <vector>
 
 #include "base/bind.h"
 #include "base/callback.h"
 #include "base/files/file_path.h"
+#include "base/logging.h"
 #include "base/macros.h"
 #include "base/memory/ptr_util.h"
 #include "base/stl_util.h"
 #include "chrome/browser/media_galleries/fileapi/media_file_system_backend.h"
 #include "chrome/browser/media_galleries/gallery_watch_manager.h"
 #include "chrome/browser/media_galleries/imported_media_gallery_registry.h"
 #include "chrome/browser/media_galleries/media_file_system_context.h"
 #include "chrome/browser/media_galleries/media_galleries_dialog_controller.h"
 #include "chrome/browser/media_galleries/media_galleries_histograms.h"
 #include "chrome/browser/media_galleries/media_galleries_preferences_factory.h"
@@ skipping 729 matching lines @@
   DISALLOW_COPY_AND_ASSIGN(MediaFileSystemContextImpl);
 };
 
 // Constructor in 'private' section because depends on private class definition.
 MediaFileSystemRegistry::MediaFileSystemRegistry()
     : file_system_context_(new MediaFileSystemContextImpl) {
   StorageMonitor::GetInstance()->AddObserver(this);
 }
 
 MediaFileSystemRegistry::~MediaFileSystemRegistry() {
-  // TODO(gbillock): This is needed because the unit test uses the
-  // g_browser_process registry. We should create one in the unit test,
-  // and then can remove this.
-  if (StorageMonitor::GetInstance())
-    StorageMonitor::GetInstance()->RemoveObserver(this);
+  DCHECK(StorageMonitor::GetInstance());
+  StorageMonitor::GetInstance()->RemoveObserver(this);
 }
 
 void MediaFileSystemRegistry::OnPermissionRemoved(
     MediaGalleriesPreferences* prefs,
     const std::string& extension_id,
     MediaGalleryPrefId pref_id) {
   Profile* profile = prefs->profile();
   ExtensionGalleriesHostMap::const_iterator host_map_it =
       extension_hosts_map_.find(profile);
   DCHECK(host_map_it != extension_hosts_map_.end());
@@ skipping 91 matching lines @@
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
 
   auto extension_hosts_it = extension_hosts_map_.find(profile);
   DCHECK(extension_hosts_it != extension_hosts_map_.end());
   extension_hosts_map_.erase(extension_hosts_it);
 
   auto profile_subscription_it = profile_subscription_map_.find(profile);
   DCHECK(profile_subscription_it != profile_subscription_map_.end());
   profile_subscription_map_.erase(profile_subscription_it);
 }