Redesigned and refactored ScopedMTPDeviceMapEntry, MTPDeviceMapService & MTPDeviceDelegate classes.

chrome/browser/media_gallery/media_file_system_registry.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.
 
 // MediaFileSystemRegistry registers pictures directories and media devices as
 // File API filesystems and keeps track of the path to filesystem ID mappings.
 
 #ifndef CHROME_BROWSER_MEDIA_GALLERY_MEDIA_FILE_SYSTEM_REGISTRY_H_
 #define CHROME_BROWSER_MEDIA_GALLERY_MEDIA_FILE_SYSTEM_REGISTRY_H_
 
 #include <map>
 #include <string>
 #include <utility>
 #include <vector>
 
 #include "base/basictypes.h"
 #include "base/lazy_instance.h"
 #include "base/file_path.h"
 #include "base/memory/ref_counted.h"
-#include "base/memory/weak_ptr.h"
 #include "base/prefs/public/pref_change_registrar.h"
 #include "base/system_monitor/system_monitor.h"
 #include "webkit/fileapi/media/mtp_device_file_system_config.h"
 
 #if defined(SUPPORT_MTP_DEVICE_FILESYSTEM)
 #include "chrome/browser/media_gallery/mtp_device_delegate_impl.h"
 #endif
 
 class Profile;
 
@@ skipping 19 matching lines @@
                       const FilePath& fs_path,
                       const std::string& filesystem_id);
   MediaFileSystemInfo();
 
   std::string name;  // JSON string, must not contain slashes.
   FilePath path;
   std::string fsid;
 };
 
 #if defined(SUPPORT_MTP_DEVICE_FILESYSTEM)
-// Class to manage MTPDeviceDelegateImpl object for the attached MTP device.
-// Refcounted to reuse the same MTP device delegate entry across extensions.
-// This class supports WeakPtr (extends SupportsWeakPtr) to expose itself as
-// a weak pointer to MediaFileSystemRegistry.
+// Class to manage the lifetime of MTPDeviceDelegateImpl object for the
+// attached media transfer protocol (MTP) device. This object is constructed
+// for each MTP device. Refcounted to reuse the same MTP device delegate entry
+// across extensions.
 class ScopedMTPDeviceMapEntry
-    : public base::RefCounted<ScopedMTPDeviceMapEntry>,
-      public base::SupportsWeakPtr<ScopedMTPDeviceMapEntry> {
+    : public base::RefCounted<ScopedMTPDeviceMapEntry> {
  public:
   // |no_references_callback| is called when the last ScopedMTPDeviceMapEntry
   // reference goes away.
   ScopedMTPDeviceMapEntry(const FilePath::StringType& device_location,
                           const base::Closure& no_references_callback);
 
  private:
   // Friend declaration for ref counted implementation.
   friend class base::RefCounted<ScopedMTPDeviceMapEntry>;
 
-  // Private because this class is ref-counted.
+  // Private because this class is ref-counted. Destructed when the last user of
+  // this MTP device is destroyed or when the MTP device is detached from the
+  // system or when the browser is in shutdown mode or when the last extension
+  // revokes the MTP device gallery permissions.
   ~ScopedMTPDeviceMapEntry();
 
-  // Store the MTP or PTP device location.
+  // The MTP or PTP device location.
   const FilePath::StringType device_location_;
 
-  // Store a raw pointer of MTPDeviceDelegateImpl object.
-  // MTPDeviceDelegateImpl is ref-counted and owned by MTPDeviceMapService.
-  // This class tells MTPDeviceMapService to dispose of it when the last
-  // reference to |this| goes away.
-  MTPDeviceDelegateImpl* delegate_;
-
   // A callback to call when the last reference of this object goes away.
   base::Closure no_references_callback_;
 
   DISALLOW_COPY_AND_ASSIGN(ScopedMTPDeviceMapEntry);
 };
 #endif
 
 class MediaFileSystemContext {
  public:
   virtual ~MediaFileSystemContext() {}
@@ skipping 55 matching lines @@
 
   // Map an extension to the ExtensionGalleriesHost.
   typedef std::map<std::string /*extension_id*/,
                    scoped_refptr<ExtensionGalleriesHost> > ExtensionHostMap;
   // Map a profile and extension to the ExtensionGalleriesHost.
   typedef std::map<Profile*, ExtensionHostMap> ExtensionGalleriesHostMap;
   // Map a profile to a PrefChangeRegistrar.
   typedef std::map<Profile*, PrefChangeRegistrar*> PrefChangeRegistrarMap;
 
 #if defined(SUPPORT_MTP_DEVICE_FILESYSTEM)
-  // Map a MTP or PTP device location to the weak pointer of
-  // ScopedMTPDeviceMapEntry.
-  typedef std::map<const FilePath::StringType,
-                   base::WeakPtr<ScopedMTPDeviceMapEntry> >
+  // Map a MTP or PTP device location to the raw pointer of
+  // ScopedMTPDeviceMapEntry. It is safe to store a raw pointer in this
+  // map.
+  typedef std::map<const FilePath::StringType, ScopedMTPDeviceMapEntry*>
       MTPDeviceDelegateMap;
 #endif
 
   // Obtain an instance of this class via GetInstance().
   MediaFileSystemRegistry();
   virtual ~MediaFileSystemRegistry();
 
   void OnMediaGalleriesRememberedGalleriesChanged(PrefServiceBase* service);
 
 #if defined(SUPPORT_MTP_DEVICE_FILESYSTEM)
@@ skipping 11 matching lines @@
                                      const std::string& extension_id);
 
   // Only accessed on the UI thread. This map owns all the
   // ExtensionGalleriesHost objects created.
   ExtensionGalleriesHostMap extension_hosts_map_;
 
   PrefChangeRegistrarMap pref_change_registrar_map_;
 
 #if defined(SUPPORT_MTP_DEVICE_FILESYSTEM)
   // Only accessed on the UI thread.
-  MTPDeviceDelegateMap mtp_delegate_map_;
+  MTPDeviceDelegateMap mtp_device_delegate_map_;
 #endif
 
   scoped_ptr<MediaFileSystemContext> file_system_context_;
 
   DISALLOW_COPY_AND_ASSIGN(MediaFileSystemRegistry);
 };
 
 }  // namespace chrome
 
 #endif  // CHROME_BROWSER_MEDIA_GALLERY_MEDIA_FILE_SYSTEM_REGISTRY_H_