Media Galleries API: Fix MediaGalleriesPreferences finders race.

chrome/browser/media_galleries/media_galleries_preferences.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_MEDIA_GALLERIES_MEDIA_GALLERIES_PREFERENCES_H_
 #define CHROME_BROWSER_MEDIA_GALLERIES_MEDIA_GALLERIES_PREFERENCES_H_
 
 #include <map>
 #include <set>
 #include <string>
 
 #include "base/basictypes.h"
+#include "base/callback_forward.h"
 #include "base/files/file_path.h"
 #include "base/memory/weak_ptr.h"
 #include "base/observer_list.h"
 #include "base/strings/string16.h"
+#include "base/threading/thread_checker.h"
 #include "base/time/time.h"
 #include "chrome/browser/storage_monitor/removable_storage_observer.h"
 #include "components/browser_context_keyed_service/browser_context_keyed_service.h"
 
 class Profile;
 
 namespace base {
 class DictionaryValue;
 }
 
@@ skipping 114 matching lines @@
 
      virtual void OnGalleryInfoUpdated(MediaGalleriesPreferences* pref,
                                        MediaGalleryPrefId pref_id) {}
     protected:
      virtual ~GalleryChangeObserver();
   };
 
   explicit MediaGalleriesPreferences(Profile* profile);
   virtual ~MediaGalleriesPreferences();
 
+  // Ensures that the preferences is initialized. The provided callback, if
+  // non-null, will be called when initialization is complete. If initialization
+  // has already completed, this callback will be invoked in the calling stack.
+  // Before the callback is run, other calls may not return the correct results.
+  // Should be invoked on the UI thread; callbacks will be run on the UI thread.
+  // This call also ensures that the StorageMonitor is initialized.
+  // Note for unit tests: This requires an active FILE thread and
+  // EnsureMediaDirectoriesExists instance to complete reliably.
+  void EnsureInitialized(base::Closure callback);
+
+  // Return true if the storage monitor has already been initialized.
+  bool IsInitialized() const;
+
   Profile* profile();
 
   void AddGalleryChangeObserver(GalleryChangeObserver* observer);
   void RemoveGalleryChangeObserver(GalleryChangeObserver* observer);
 
   // RemovableStorageObserver implementation.
   virtual void OnRemovableStorageAttached(const StorageInfo& info) OVERRIDE;
 
   // Lookup a media gallery and fill in information about it and return true if
   // it exists. Return false if it does not, filling in default information.
@@ skipping 33 matching lines @@
   // Removes the gallery identified by |id| from the store.
   void ForgetGalleryById(MediaGalleryPrefId id);
 
   MediaGalleryPrefIdSet GalleriesForExtension(
       const extensions::Extension& extension) const;
 
   void SetGalleryPermissionForExtension(const extensions::Extension& extension,
                                         MediaGalleryPrefId pref_id,
                                         bool has_permission);
 
-  const MediaGalleriesPrefInfoMap& known_galleries() const {
-    return known_galleries_;
-  }
+  const MediaGalleriesPrefInfoMap& known_galleries() const;
 
   // BrowserContextKeyedService implementation:
   virtual void Shutdown() OVERRIDE;
 
   static void RegisterProfilePrefs(user_prefs::PrefRegistrySyncable* registry);
 
   // Returns true if the media gallery preferences system has ever been used
   // for this profile. To be exact, it checks if a gallery has ever been added
   // (including defaults).
   static bool APIHasBeenUsed(Profile* profile);
 
  private:
   friend class MediaGalleriesPreferencesTest;
   friend class MediaGalleriesPermissionsTest;
 
   typedef std::map<std::string /*device id*/, MediaGalleryPrefIdSet>
       DeviceIdPrefIdsMap;
 
+  // These must be called on the UI thread.
+  void OnInitializationCallbackReturned();
+  void FinishInitialization();
+
   // Populates the default galleries if this is a fresh profile.
   void AddDefaultGalleriesIfFreshProfile();
 
   // This is a hack - Some devices (iTunes, Picasa) are singletons in that only
   // one instance of that type is supported at a time. As such, the device id
   // should just be "itunes:" or "picasa:" but that would mean finding the
   // location of the database file multiple times, which may be an async
   // operation. Storing the location of the backing database in the device
   // id allows that look up to be avoided. However, the cost is that if the
   // database moves, the device id in preferences has to be updated.  This
   // method searches for a gallery of the type passed in and updates its
   // device id.  It returns true if the device id is up to date.
   bool UpdateDeviceIDForSingletonType(const std::string& device_id);
 
-  // Try to add an entry for the iTunes 'device'.
-  void OnITunesDeviceID(const std::string& device_id);
-
-  // Try to add an entry for the Picasa 'device'.
-  void OnPicasaDeviceID(const std::string& device_id);
+  // Handle an iTunes or Picasa finder returning a device ID to us.
+  void OnFinderDeviceID(const std::string& device_id);
 
   // Builds |known_galleries_| from the persistent store.
   void InitFromPrefs();
 
   MediaGalleryPrefId AddGalleryInternal(const std::string& device_id,
                                         const string16& display_name,
                                         const base::FilePath& relative_path,
                                         bool user_added,
                                         const string16& volume_label,
                                         const string16& vendor_name,
@@ skipping 27 matching lines @@
   // Get the ExtensionPrefs to use; this will be either the ExtensionPrefs
   // object associated with |profile_|, or extension_prefs_for_testing_, if
   // SetExtensionPrefsForTesting() has been called.
   extensions::ExtensionPrefs* GetExtensionPrefs() const;
 
   // Set the ExtensionPrefs object to be returned by GetExtensionPrefs().
   void SetExtensionPrefsForTesting(extensions::ExtensionPrefs* extension_prefs);
 
   base::WeakPtrFactory<MediaGalleriesPreferences> weak_factory_;
 
+  // Used to make sure we call initialize from the same thread as creation.
+  base::ThreadChecker thread_checker_;

[Lei Zhang, 2013/09/21 00:36:06]

If we know MediaGalleriesPreferences must run on the UI thread, just check for
that instead.

[tommycli, 2013/09/23 20:39:12]

Done.

+
+  bool initializing_;
+  bool initialized_;
+  std::vector<base::Closure> on_initialize_callbacks_;
+  int pre_initialization_callbacks_waiting_;
+
   // The profile that owns |this|.
   Profile* profile_;
 
   // The ExtensionPrefs used in a testing environment, where
   // BrowserContextKeyedServices aren't used. This will be NULL unless it is
   // set with SetExtensionPrefsForTesting().
   extensions::ExtensionPrefs* extension_prefs_for_testing_;
 
   // An in-memory cache of known galleries.
   MediaGalleriesPrefInfoMap known_galleries_;
 
   // A mapping from device id to the set of gallery pref ids on that device.
   // All pref ids in |device_map_| are also in |known_galleries_|.
   DeviceIdPrefIdsMap device_map_;
 
   ObserverList<GalleryChangeObserver> gallery_change_observers_;
 
   DISALLOW_COPY_AND_ASSIGN(MediaGalleriesPreferences);
 };
 
 #endif  // CHROME_BROWSER_MEDIA_GALLERIES_MEDIA_GALLERIES_PREFERENCES_H_