Connect MediaFileSystemRegistry with MediaGalleriesPreferences

chrome/browser/media_gallery/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.
 
 // MediaFileSystemRegistry implementation.
 
 #include "chrome/browser/media_gallery/media_file_system_registry.h"
 
 #include <set>
 
+#include "base/callback.h"
 #include "base/file_path.h"
 #include "base/path_service.h"
 #include "base/system_monitor/system_monitor.h"
 #include "base/utf_string_conversions.h"
+#include "chrome/browser/media_gallery/media_galleries_preferences.h"
+#include "chrome/browser/media_gallery/media_galleries_preferences_factory.h"
 #include "chrome/browser/media_gallery/media_storage_util.h"
+#include "chrome/browser/profiles/profile.h"
 #include "chrome/common/chrome_paths.h"
 #include "chrome/common/extensions/extension_constants.h"
 #include "chrome/common/extensions/extension.h"
 #include "content/public/browser/browser_thread.h"
+#include "content/public/browser/notification_observer.h"
+#include "content/public/browser/notification_registrar.h"
 #include "content/public/browser/notification_source.h"
 #include "content/public/browser/notification_types.h"
 #include "content/public/browser/render_process_host.h"
+#include "content/public/browser/render_view_host.h"
+#include "content/public/browser/web_contents.h"
 #include "webkit/fileapi/file_system_types.h"
 #include "webkit/fileapi/isolated_context.h"
 #include "webkit/fileapi/media/media_file_system_config.h"
 
 #if defined(SUPPORT_MEDIA_FILESYSTEM)
 #include "webkit/fileapi/media/media_device_map_service.h"
-
-using fileapi::MediaDeviceMapService;
 #endif
 
 namespace chrome {
 
 static base::LazyInstance<MediaFileSystemRegistry>::Leaky
     g_media_file_system_registry = LAZY_INSTANCE_INITIALIZER;
 
 using base::SystemMonitor;
 using content::BrowserThread;
+using content::NavigationController;
 using content::RenderProcessHost;
+using content::WebContents;
 using fileapi::IsolatedContext;
 
 namespace {
 
-bool IsGalleryPermittedForExtension(const extensions::Extension& extension,
-                                    const FilePath::StringType& location) {
-  if (extension.HasAPIPermission(
-        extensions::APIPermission::kMediaGalleriesAllGalleries)) {
-    return true;
-  }
-  // TODO(vandebo) Check with prefs for permission to this gallery.
-  return false;
+struct InvalidatedGallery {

[Lei Zhang, 2012/09/04 23:38:51]

Move this to inside MediaFileSystemRegistry::OnRemovableStorageDetached() since
it's only used there?

[vandebo (ex-Chrome), 2012/09/05 00:58:12]

I did try that originally, but the compiler complains: "template argument ...
uses local type"
Googling says '§14.3.1/2 from the 2003 C++ Standard: A local type, a type with
no linkage, an unnamed type or a type compounded from any of these types shall
not be used as a template-argument for a template type-parameter.'

+  ExtensionGalleriesHost* extension_host;
+  MediaGalleryPrefId pref_id;
+};
+
+typedef std::list<InvalidatedGallery> InvalidatedGalleries;

[Lei Zhang, 2012/09/04 23:38:51]

nit: #include <list>

[vandebo (ex-Chrome), 2012/09/05 00:58:12]

Done.

+
+std::string RegisterFileSystem(std::string device_id, const FilePath& path) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+
+  IsolatedContext* isolated_context = IsolatedContext::GetInstance();
+  if (MediaStorageUtil::IsMassStorageDevice(device_id)) {
+    // Sanity checks for |path|.
+    CHECK(path.IsAbsolute());
+    CHECK(!path.ReferencesParent());
+    std::string fs_name(extension_misc::kMediaFileSystemPathPart);
+    const std::string fsid = isolated_context->RegisterFileSystemForPath(
+        fileapi::kFileSystemTypeNativeMedia, path, &fs_name);
+    CHECK(!fsid.empty());
+    return fsid;
+  }
+
+  // TODO(kmadhusu) handle MTP devices.
+  NOTREACHED();
+  return std::string();
 }
 
 }  // namespace
 
+// Refcounted only so it can easily be put in map. All instances are owned
+// by |MediaFileSystemRegistry::extension_hosts_map_|.
+class ExtensionGalleriesHost
+    : public base::RefCounted<ExtensionGalleriesHost>,
+      public content::NotificationObserver {
+ public:
+  // |no_references_callback| is called when the last RenderViewHost reference
+  // goes away. RenderViewHost references are added through ReferenceFromRVH().
+  explicit ExtensionGalleriesHost(const base::Closure& no_references_callback)
+      : no_references_callback_(no_references_callback) {
+  }
+
+  // For each galelry in the list of permitted |galleries|, looks up or creates

[Lei Zhang, 2012/09/04 23:38:51]

nit: typo

[vandebo (ex-Chrome), 2012/09/05 00:58:12]

Done.

+  // a file system id and returns the information needed for the renderer to
+  // create those file system objects.
+  std::vector<MediaFileSystemRegistry::MediaFSInfo> GetMediaFileSystems(
+      const MediaGalleryPrefIdSet& galleries,
+      const MediaGalleriesPrefInfoMap& galleries_info) {
+    std::vector<MediaFileSystemRegistry::MediaFSInfo> result;
+    for (std::set<MediaGalleryPrefId>::const_iterator id = galleries.begin();
+         id != galleries.end();
+         ++id) {
+      // TODO(vandebo) we also need to check that these galleries are attached.
+      PrefIdFsInfoMap::const_iterator existing_info = pref_id_map_.find(*id);
+      if (existing_info != pref_id_map_.end()) {
+        result.push_back(existing_info->second);
+        continue;
+      }
+      const MediaGalleryPrefInfo& gallery_info =
+          galleries_info.find(*id)->second;
+      const std::string& device_id = gallery_info.device_id;
+      // TODO(kmadhusu) handle MTP devices.
+      DCHECK(MediaStorageUtil::IsMassStorageDevice(device_id));
+      FilePath path = MediaStorageUtil::FindDevicePathById(device_id);
+      CHECK(!path.empty());
+      path = path.Append(gallery_info.path);
+
+      MediaFileSystemRegistry::MediaFSInfo new_entry;
+      new_entry.name = gallery_info.display_name;
+      new_entry.path = path;
+      new_entry.fsid = RegisterFileSystem(device_id, path);
+      result.push_back(new_entry);
+      pref_id_map_[*id] = new_entry;
+    }
+
+    // TODO(vandebo) We need a way of getting notification when permission for
+    // galleries are revoked (http://crbug.com/145855).  For now, invalidate
+    // any fsid we have that we didn't get this time around.
+    if (galleries.size() != pref_id_map_.size()) {
+      MediaGalleryPrefIdSet old_galleries;
+      for (PrefIdFsInfoMap::const_iterator it = pref_id_map_.begin();
+           it != pref_id_map_.end();
+           ++it) {
+        old_galleries.insert(it->first);
+      }
+      MediaGalleryPrefIdSet invalid_galleries;
+      std::set_difference(old_galleries.begin(), old_galleries.end(),
+                          galleries.begin(), galleries.end(),
+                          std::inserter(invalid_galleries,
+                                        invalid_galleries.begin()));
+      for (MediaGalleryPrefIdSet::const_iterator it = invalid_galleries.begin();
+           it != invalid_galleries.end();
+           ++it) {
+        RevokeGalleryByPrefId(*it);
+      }
+    }
+
+    return result;
+  }
+
+  // Revoke the file system for |id| if this extension has created one for |id|.
+  void RevokeGalleryByPrefId(MediaGalleryPrefId id) {
+    PrefIdFsInfoMap::iterator gallery = pref_id_map_.find(id);
+    if (gallery == pref_id_map_.end())

[Lei Zhang, 2012/09/04 23:38:51]

Can this ever happen?

[vandebo (ex-Chrome), 2012/09/05 00:58:12]

Yes.  If an extension doesn't have access to a removable device (i.e. not all
galleries) and it gets unplugged,
MediaFileSystemRegistry::OnRemovableStorageDetached will call this.

+      return;
+
+    IsolatedContext* isolated_context = IsolatedContext::GetInstance();
+    isolated_context->RevokeFileSystem(gallery->second.fsid);
+
+    pref_id_map_.erase(gallery);
+  }
+
+  // Indicate that the passed render process will reference the file system

[Lei Zhang, 2012/09/04 23:38:51]

render process -> rvh

[vandebo (ex-Chrome), 2012/09/05 00:58:12]

Done.

+  // ids created by this class.  It is safe to call this multiple times with
+  // the same RVH.
+  void ReferenceFromRVH(const content::RenderViewHost* rvh) {
+    WebContents* contents = WebContents::FromRenderViewHost(rvh);
+    if (registrar_.IsRegistered(this,
+                                content::NOTIFICATION_WEB_CONTENTS_DESTROYED,
+                                content::Source<WebContents>(contents))) {
+      return;
+    }
+    registrar_.Add(this, content::NOTIFICATION_WEB_CONTENTS_DESTROYED,
+                   content::Source<WebContents>(contents));
+    registrar_.Add(
+        this, content::NOTIFICATION_NAV_ENTRY_COMMITTED,
+        content::Source<NavigationController>(&contents->GetController()));
+
+    RenderProcessHost* rph = contents->GetRenderProcessHost();
+    rph_refs_[rph].insert(contents);
+    if (rph_refs_[rph].size() == 1) {
+      registrar_.Add(this, content::NOTIFICATION_RENDERER_PROCESS_CLOSED,
+                     content::Source<RenderProcessHost>(rph));
+    }
+  }
+
+  // NotificationObserver implementation.
+  virtual void Observe(int type,
+                       const content::NotificationSource& source,
+                       const content::NotificationDetails& details) OVERRIDE {
+    switch (type) {
+      case content::NOTIFICATION_RENDERER_PROCESS_CLOSED: {
+        OnRendererProcessClosed(
+            content::Source<RenderProcessHost>(source).ptr());
+        break;
+      }
+      case content::NOTIFICATION_WEB_CONTENTS_DESTROYED: {
+        OnWebContentsDestroyedOrNavigated(
+            content::Source<WebContents>(source).ptr());
+        break;
+      }
+      case content::NOTIFICATION_NAV_ENTRY_COMMITTED: {
+        NavigationController* controller =
+            content::Source<NavigationController>(source).ptr();
+        WebContents* contents = controller->GetWebContents();
+        OnWebContentsDestroyedOrNavigated(contents);
+        break;
+      }
+      default: {
+        NOTREACHED();
+        break;
+      }
+    }
+  }
+
+ private:
+  typedef std::map<MediaGalleryPrefId, MediaFileSystemRegistry::MediaFSInfo>
+      PrefIdFsInfoMap;
+  typedef std::map<const RenderProcessHost*, std::set<const WebContents*> >
+      RenderProcessHostRefCount;
+
+  // Private destructor and friend declaration for ref counted implementation.
+  friend class base::RefCounted<ExtensionGalleriesHost>;

[Lei Zhang, 2012/09/04 23:38:51]

nit: blan line after this

[vandebo (ex-Chrome), 2012/09/05 00:58:12]

Done.

+  virtual ~ExtensionGalleriesHost() {
+    DCHECK(rph_refs_.empty());
+    DCHECK(pref_id_map_.empty());
+  }
+
+  void OnRendererProcessClosed(const RenderProcessHost* rph) {
+    RenderProcessHostRefCount::const_iterator rph_info = rph_refs_.find(rph);
+    DCHECK(rph_info != rph_refs_.end());
+    // We're going to remove everything from the set, so we make a copy
+    // before operating on it.
+    std::set<const WebContents*> dead_rvhs = rph_info->second;

[Lei Zhang, 2012/09/04 23:38:51]

|dead_rvhs| is weirdly named, since it's a set of WebContents.

[vandebo (ex-Chrome), 2012/09/05 00:58:12]

Done.

+    DCHECK(!dead_rvhs.empty());
+
+    for (std::set<const WebContents*>::const_iterator it = dead_rvhs.begin();
+         it != dead_rvhs.end();
+         ++it) {
+      OnWebContentsDestroyedOrNavigated(*it);
+    }
+    DCHECK(rph_refs_.find(rph) == rph_refs_.end());

[Lei Zhang, 2012/09/04 23:38:51]

You can use ContainsKey() here.

[vandebo (ex-Chrome), 2012/09/05 00:58:12]

Done.

+  }
+
+  void OnWebContentsDestroyedOrNavigated(const WebContents* contents) {
+    registrar_.Remove(this, content::NOTIFICATION_WEB_CONTENTS_DESTROYED,
+                      content::Source<WebContents>(contents));
+    registrar_.Remove(
+        this, content::NOTIFICATION_NAV_ENTRY_COMMITTED,
+        content::Source<NavigationController>(&contents->GetController()));
+
+    RenderProcessHost* rph = contents->GetRenderProcessHost();
+    rph_refs_[rph].erase(contents);
+    if (rph_refs_[rph].empty()) {
+      registrar_.Remove(this, content::NOTIFICATION_RENDERER_PROCESS_CLOSED,
+                        content::Source<RenderProcessHost>(rph));
+      rph_refs_.erase(rph);
+    }
+
+    if (rph_refs_.empty()) {
+      IsolatedContext* isolated_context = IsolatedContext::GetInstance();
+      for (PrefIdFsInfoMap::const_iterator it = pref_id_map_.begin();
+           it != pref_id_map_.end();
+           ++it) {
+        isolated_context->RevokeFileSystem(it->second.fsid);
+      }
+      pref_id_map_.clear();
+      no_references_callback_.Run();
+    }
+  }
+
+  // A callback to call when the last RVH reference goes away.
+  base::Closure no_references_callback_;
+
+  // A map from the gallery preferences id to the file system information.
+  PrefIdFsInfoMap pref_id_map_;
+
+  // The set of render processes and web contents that may have references to
+  // the file system ids this instance manages.
+  RenderProcessHostRefCount rph_refs_;
+
+  // A registrar for listening notifications.
+  content::NotificationRegistrar registrar_;
+
+  DISALLOW_COPY_AND_ASSIGN(ExtensionGalleriesHost);
+};
 
 /******************
  * Public methods
  ******************/
 
 // static
 MediaFileSystemRegistry* MediaFileSystemRegistry::GetInstance() {
   return g_media_file_system_registry.Pointer();
 }
 
+// TODO(vandebo) We need to make this async so that we check that the
+// galleries are attached (requires the file thread).
 std::vector<MediaFileSystemRegistry::MediaFSInfo>
 MediaFileSystemRegistry::GetMediaFileSystemsForExtension(
-    const content::RenderProcessHost* rph,
-    const extensions::Extension& extension) {
+    const content::RenderViewHost* rvh,
+    const extensions::Extension* extension) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 
-  std::vector<MediaFSInfo> results;
-  std::pair<ChildIdToMediaFSMap::iterator, bool> ret =
-      media_fs_map_.insert(std::make_pair(rph, MediaPathToFSIDMap()));
-  ChildIdToMediaFSMap::iterator& child_it = ret.first;
-  if (ret.second) {
-    // Never seen a GetMediaFileSystems call from this RPH. Initialize its
-    // file system mappings.
-    RegisterForRPHGoneNotifications(rph);
-    FilePath pictures_path;
-    // TODO(vandebo) file system galleries need a unique id as well.
-    if (PathService::Get(chrome::DIR_USER_PICTURES, &pictures_path) &&
-        IsGalleryPermittedForExtension(extension, pictures_path.value())) {
-      std::string fsid = RegisterPathAsFileSystem(pictures_path);
-      child_it->second.insert(std::make_pair(pictures_path, fsid));
-    }
+  Profile* profile =
+      Profile::FromBrowserContext(rvh->GetProcess()->GetBrowserContext());
+  MediaGalleriesPreferences* preferences =
+      MediaGalleriesPreferencesFactory::GetForProfile(profile);
+  MediaGalleryPrefIdSet galleries =
+      preferences->GalleriesForExtension(*extension);
+  ExtensionGalleriesHost* extension_host =
+      extension_hosts_map_[profile][extension->id()].get();
+
+  if (galleries.empty() && !extension_host)

[Lei Zhang, 2012/09/04 23:38:51]

Can you comment what this case means?
"Never had access to / tried to access any galleries and still has no access to
any galleries".

[vandebo (ex-Chrome), 2012/09/05 00:58:12]

Done.

+    return std::vector<MediaFileSystemRegistry::MediaFSInfo>();
+
+  if (!extension_host) {

[Lei Zhang, 2012/09/04 23:38:51]

ditto, please comment.
"Has access to galleries, but has never accessed before."

[vandebo (ex-Chrome), 2012/09/05 00:58:12]

I'm not sure this chunk of code needs a comment.... If we don't have an
extension galleries host, we make one.  Any thoughts on a comment that doesn't
just repeat what the code says?

+    extension_hosts_map_[profile][extension->id()] =
+        new ExtensionGalleriesHost(
+            base::Bind(&MediaFileSystemRegistry::OnExtensionGalleriesHostEmpty,
+                       base::Unretained(this), profile, extension->id()));
+    extension_host = extension_hosts_map_[profile][extension->id()].get();
   }
+  extension_host->ReferenceFromRVH(rvh);
 
-  // TODO(thestig) Handle overlap between devices and media directories.
-  SystemMonitor* monitor = SystemMonitor::Get();
-  const std::vector<SystemMonitor::RemovableStorageInfo> media_devices =
-      monitor->GetAttachedRemovableStorage();
-  for (size_t i = 0; i < media_devices.size(); ++i) {
-    MediaStorageUtil::Type type;
-    MediaStorageUtil::CrackDeviceId(media_devices[i].device_id, &type, NULL);
-    // TODO(vandebo) Handle MTP devices.
-    if (type != MediaStorageUtil::MTP_OR_PTP &&
-        IsGalleryPermittedForExtension(extension, media_devices[i].location)) {
-      device_id_map_.insert(std::make_pair(media_devices[i].device_id,
-                                           media_devices[i]));
-      FilePath path(media_devices[i].location);
-      const std::string fsid = RegisterPathAsFileSystem(path);
-      child_it->second.insert(std::make_pair(path, fsid));
-    }
-  }
-
-  MediaPathToFSIDMap& child_map = child_it->second;
-  for (MediaPathToFSIDMap::const_iterator it = child_map.begin();
-       it != child_map.end();
-       ++it) {
-    MediaFSInfo entry;
-    // TODO(vandebo) use a better name, fsid for now.
-    entry.name = it->second;
-    entry.fsid = it->second;
-    entry.path = it->first;
-    results.push_back(entry);
-  }
-  return results;
+  return extension_host->GetMediaFileSystems(galleries,
+                                             preferences->known_galleries());
 }
 
+// TODO(vandebo) We also need to listen for the attach event and add newly
+// attached media devices to MediaGalleriesPreferences.
 void MediaFileSystemRegistry::OnRemovableStorageDetached(
     const std::string& id) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 
-  DeviceIdToInfoMap::iterator it = device_id_map_.find(id);
-  if (it == device_id_map_.end())
-    return;
+  // Since revoking a gallery in the ExtensionGalleriesHost may cause it
+  // to be removed from the map and therefore invalidate any iterator pointing
+  // to it, we first make a list of all the ExtensionGalleriesHost*, pref_id
+  // pairs to invalidate and then invalidate them in a second step.
+  InvalidatedGalleries invalidated_galleries;
 
-  FilePath path(it->second.location);
-  RevokeMediaFileSystem(path);
-  device_id_map_.erase(it);
-}
+  for (ExtensionGalleriesHostMap::iterator extension_hosts_map_it =
+           extension_hosts_map_.begin();
+       extension_hosts_map_it != extension_hosts_map_.end();
+       ++extension_hosts_map_it) {
+    MediaGalleriesPreferences* preferences =
+        MediaGalleriesPreferencesFactory::GetForProfile(
+            extension_hosts_map_it->first);
+    MediaGalleryPrefIdSet detached_galleries =
+        preferences->LookUpGalleriesByDeviceId(id);
+    for (ExtensionHostMap::const_iterator extension_host_it =

[Lei Zhang, 2012/09/04 23:38:51]

Do you think it'll be cleaner to put the second and third for-loop into a helper
function?

[vandebo (ex-Chrome), 2012/09/05 00:58:12]

I realized that this code was inefficient in that it stores the exploded state
(profiles x extension_hosts x pref_ids).  I changed it to use less space, which
moves some of the loops around.  I also made the iterators names more readable. 
Let me know what you think about abstracting any of it to improve readability.

+             extension_hosts_map_it->second.begin();
+         extension_host_it != extension_hosts_map_it->second.end();
+         ++extension_host_it) {
+      for (MediaGalleryPrefIdSet::const_iterator pref_id =
+               detached_galleries.begin();
+           pref_id != detached_galleries.end();
+           ++pref_id) {
+        InvalidatedGallery gallery;
+        gallery.extension_host = extension_host_it->second.get();
+        gallery.pref_id = *pref_id;
+        invalidated_galleries.push_back(gallery);
+      }
+    }
+  }
 
-void MediaFileSystemRegistry::Observe(
-    int type,
-    const content::NotificationSource& source,
-    const content::NotificationDetails& details) {
-  DCHECK(type == content::NOTIFICATION_RENDERER_PROCESS_CLOSED ||
-         type == content::NOTIFICATION_RENDERER_PROCESS_TERMINATED);
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-  const RenderProcessHost* rph =
-      content::Source<content::RenderProcessHost>(source).ptr();
-  ChildIdToMediaFSMap::iterator child_it = media_fs_map_.find(rph);
-  CHECK(child_it != media_fs_map_.end());
-  // No need to revoke the isolated file systems. The RPH will do that.
-  media_fs_map_.erase(child_it);
-  UnregisterForRPHGoneNotifications(rph);
+  // TODO(kmadhusu, vandebo): Clean up this code. http://crbug.com/140340.
+  DCHECK(MediaStorageUtil::IsMassStorageDevice(id));
+  for (InvalidatedGalleries::const_iterator it = invalidated_galleries.begin();
+       it != invalidated_galleries.end();
+       ++it) {
+    it->extension_host->RevokeGalleryByPrefId(it->pref_id);
+  }
 }
 
 /******************
  * Private methods
  ******************/
 
 MediaFileSystemRegistry::MediaFileSystemRegistry() {
   // SystemMonitor may be NULL in unit tests.
   SystemMonitor* system_monitor = SystemMonitor::Get();
   if (system_monitor)
     system_monitor->AddDevicesChangedObserver(this);
+  // TODO(vandebo) We should add all the currently attached media devices
+  // to MediaGalleriesPreferences here.
 }
 
 MediaFileSystemRegistry::~MediaFileSystemRegistry() {
   // SystemMonitor may be NULL in unit tests.
   SystemMonitor* system_monitor = SystemMonitor::Get();
   if (system_monitor)
     system_monitor->RemoveDevicesChangedObserver(this);
 }
 
-void MediaFileSystemRegistry::RegisterForRPHGoneNotifications(
-    const content::RenderProcessHost* rph) {
-  registrar_.Add(this, content::NOTIFICATION_RENDERER_PROCESS_TERMINATED,
-                 content::Source<RenderProcessHost>(rph));
-  registrar_.Add(this, content::NOTIFICATION_RENDERER_PROCESS_CLOSED,
-                 content::Source<RenderProcessHost>(rph));
-}
-
-void MediaFileSystemRegistry::UnregisterForRPHGoneNotifications(
-    const content::RenderProcessHost* rph) {
-  registrar_.Remove(this, content::NOTIFICATION_RENDERER_PROCESS_TERMINATED,
-                    content::Source<RenderProcessHost>(rph));
-  registrar_.Remove(this, content::NOTIFICATION_RENDERER_PROCESS_CLOSED,
-                    content::Source<RenderProcessHost>(rph));
-}
-
-std::string MediaFileSystemRegistry::RegisterPathAsFileSystem(
-    const FilePath& path) {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-
-  // Sanity checks for |path|.
-  CHECK(path.IsAbsolute());
-  CHECK(!path.ReferencesParent());
-
-  // The directory name is not exposed to the js layer and we simply use
-  // a fixed name (as we only register a single directory per file system).
-  std::string register_name(extension_misc::kMediaFileSystemPathPart);
-  const std::string fsid =
-      IsolatedContext::GetInstance()->RegisterFileSystemForPath(
-          fileapi::kFileSystemTypeNativeMedia, path, &register_name);
-  CHECK(!fsid.empty());
-  return fsid;
-}
-
-void MediaFileSystemRegistry::RevokeMediaFileSystem(const FilePath& path) {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-
-  IsolatedContext* isolated_context = IsolatedContext::GetInstance();
-  isolated_context->RevokeFileSystemByPath(path);
-
-  for (ChildIdToMediaFSMap::iterator child_it = media_fs_map_.begin();
-       child_it != media_fs_map_.end();
-       ++child_it) {
-    MediaPathToFSIDMap& child_map = child_it->second;
-    MediaPathToFSIDMap::iterator media_path_it = child_map.find(path);
-    if (media_path_it == child_map.end())
-      continue;
-
-    child_map.erase(media_path_it);
-  }
+void MediaFileSystemRegistry::OnExtensionGalleriesHostEmpty(
+    Profile* profile, const std::string& extension_id) {

[Lei Zhang, 2012/09/04 23:38:51]

Also DCHECK this is on the UI thread since we access |extension_hosts_map_|
here.

[vandebo (ex-Chrome), 2012/09/05 00:58:12]

Done.

+  ExtensionGalleriesHostMap::iterator extension_hosts =
+      extension_hosts_map_.find(profile);
+  DCHECK(extension_hosts != extension_hosts_map_.end());
+  ExtensionHostMap::size_type erase_count =
+      extension_hosts->second.erase(extension_id);
+  DCHECK_EQ(1U, erase_count);
+  if (extension_hosts->second.empty())
+    extension_hosts_map_.erase(profile);
 }
 
 }  // namespace chrome