[Media Galleries] Lazily initialize the storage monitor.

chrome/browser/storage_monitor/storage_monitor.h

 // 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.
 
 #ifndef CHROME_BROWSER_STORAGE_MONITOR_STORAGE_MONITOR_H_
 #define CHROME_BROWSER_STORAGE_MONITOR_STORAGE_MONITOR_H_
 
 #include <map>
 #include <string>
 #include <vector>
@@ skipping 21 matching lines @@
 class MediaFileSystemRegistryTest;
 class RemovableStorageObserver;
 class TransientDeviceIds;
 
 // Base class for platform-specific instances watching for removable storage
 // attachments/detachments.
 // Lifecycle contracts: This class is created by ChromeBrowserMain
 // implementations before the profile is initialized, so listeners can be
 // created during profile construction. The platform-specific initialization,
 // which can lead to calling registered listeners with notifications of
-// attached volumes, will happen after profile construction.
+// attached volumes, are done lazily at first use through the async
+// |Initialize()| method. That must be done before any of the registered
+// listeners will receive updates or calls to other API methods return
+// meaningful results.
+// A post-initialization |GetAttachedStorage()| call coupled with a
+// registered listener will receive a complete set, albeit potentially with
+// duplicates. This is because there's no tracking between when listeners were
+// registered and the state of initialization, and the fact that platforms
+// behave differently in how these notifications are provided.
 class StorageMonitor {
  public:
   // This interface is provided to generators of storage notifications.
   class Receiver {
    public:
     virtual ~Receiver();
 
     virtual void ProcessAttach(const StorageInfo& info) = 0;
     virtual void ProcessDetach(const std::string& id) = 0;
     virtual void MarkInitialized() = 0;
@@ skipping 93 matching lines @@
   typedef std::map<std::string, StorageInfo> RemovableStorageMap;
 
   void ProcessAttach(const StorageInfo& storage);
   void ProcessDetach(const std::string& id);
 
   scoped_ptr<Receiver> receiver_;
 
   scoped_refptr<ObserverListThreadSafe<RemovableStorageObserver> >
       observer_list_;
 
+  // Used to make sure we call initialize from the same thread as creation.
+  base::ThreadChecker thread_checker_;
+
+  bool initializing_;
   bool initialized_;
   std::vector<base::Closure> on_initialize_callbacks_;
 
   // For manipulating removable_storage_map_ structure.
   mutable base::Lock storage_lock_;
 
   // Map of all the attached removable storage devices.
   RemovableStorageMap storage_map_;
 
   scoped_ptr<TransientDeviceIds> transient_device_ids_;
 };
 
 }  // namespace chrome
 
 #endif  // CHROME_BROWSER_STORAGE_MONITOR_STORAGE_MONITOR_H_