Revert 260276 "Change media galleries to external file system ty..."

> Change media galleries to external file system type to add toURL support
> 
> BUG=160900
> R=creis@chromium.org, joi@chromium.org, thestig@chromium.org, tsepez@chromium.org, tzik@chromium.org
> 
> Review URL: https://codereview.chromium.org/185393012

TBR=vandebo@chromium.org

Review URL: https://codereview.chromium.org/244253008

git-svn-id: svn://svn.chromium.org/chrome/branches/1916/src@265087 0039d316-1c4b-4281-b951-d872f2087c98

30 files changed, 263 insertions, 748 deletions

diff --git a/chrome/browser/chrome_content_browser_client.cc b/chrome/browser/chrome_content_browser_client.cc
index 2f5b3a5..50a0d93d 100644
--- a/chrome/browser/chrome_content_browser_client.cc
+++ b/chrome/browser/chrome_content_browser_client.cc
@@ -2567,10 +2567,6 @@ void ChromeContentBrowserClient::GetAdditionalAllowedSchemesForFileSystem(
 
 void ChromeContentBrowserClient::GetURLRequestAutoMountHandlers(
     std::vector<fileapi::URLRequestAutoMountHandler>* handlers) {
-#if !defined(OS_ANDROID)
-  handlers->push_back(
-      base::Bind(MediaFileSystemBackend::AttemptAutoMountForURLRequest));
-#endif  // OS_ANDROID
 }
 
 void ChromeContentBrowserClient::GetAdditionalFileSystemBackends(
diff --git a/chrome/browser/extensions/api/media_galleries/media_galleries_api.cc b/chrome/browser/extensions/api/media_galleries/media_galleries_api.cc
index a929d3e..6e16654 100644
--- a/chrome/browser/extensions/api/media_galleries/media_galleries_api.cc
+++ b/chrome/browser/extensions/api/media_galleries/media_galleries_api.cc
@@ -176,11 +176,11 @@ base::ListValue* ConstructFileSystemList(
     if (has_read_permission) {
       content::ChildProcessSecurityPolicy* policy =
           content::ChildProcessSecurityPolicy::GetInstance();
-      policy->GrantReadFile(child_id, filesystems[i].path);
+      policy->GrantReadFileSystem(child_id, filesystems[i].fsid);
       if (has_delete_permission) {
-        policy->GrantDeleteFrom(child_id, filesystems[i].path);
+        policy->GrantDeleteFromFileSystem(child_id, filesystems[i].fsid);
         if (has_copy_to_permission) {
-          policy->GrantCopyInto(child_id, filesystems[i].path);
+          policy->GrantCopyIntoFileSystem(child_id, filesystems[i].fsid);
         }
       }
     }
diff --git a/chrome/browser/extensions/api/media_galleries/media_galleries_apitest.cc b/chrome/browser/extensions/api/media_galleries/media_galleries_apitest.cc
index 45a1a5f..e2f9070 100644
--- a/chrome/browser/extensions/api/media_galleries/media_galleries_apitest.cc
+++ b/chrome/browser/extensions/api/media_galleries/media_galleries_apitest.cc
@@ -195,7 +195,7 @@ class MediaGalleriesPlatformAppBrowserTest : public PlatformAppBrowserTest {
   // This function makes a single fake gallery. This is needed to test platforms
   // with no default media galleries, such as CHROMEOS. This fake gallery is
   // pre-populated with a test.jpg and test.txt.
-  void MakeSingleFakeGallery(MediaGalleryPrefId* pref_id) {
+  void MakeSingleFakeGallery() {
     ASSERT_FALSE(fake_gallery_temp_dir_.IsValid());
     ASSERT_TRUE(fake_gallery_temp_dir_.CreateUniqueTempDir());
 
@@ -204,18 +204,15 @@ class MediaGalleriesPlatformAppBrowserTest : public PlatformAppBrowserTest {
     MediaGalleryPrefInfo gallery_info;
     ASSERT_FALSE(preferences->LookUpGalleryByPath(fake_gallery_temp_dir_.path(),
                                                   &gallery_info));
-    MediaGalleryPrefId id = preferences->AddGallery(
-        gallery_info.device_id,
-        gallery_info.path,
-        MediaGalleryPrefInfo::kAutoDetected,
-        gallery_info.volume_label,
-        gallery_info.vendor_name,
-        gallery_info.model_name,
-        gallery_info.total_size_in_bytes,
-        gallery_info.last_attach_time,
-        0, 0, 0);
-    if (pref_id)
-      *pref_id = id;
+    preferences->AddGallery(gallery_info.device_id,
+                            gallery_info.path,
+                            MediaGalleryPrefInfo::kAutoDetected,
+                            gallery_info.volume_label,
+                            gallery_info.vendor_name,
+                            gallery_info.model_name,
+                            gallery_info.total_size_in_bytes,
+                            gallery_info.last_attach_time,
+                            0, 0, 0);
 
     content::RunAllPendingInMessageLoop();
 
@@ -430,7 +427,7 @@ class MediaGalleriesPlatformAppBrowserTest : public PlatformAppBrowserTest {
 #endif
 IN_PROC_BROWSER_TEST_F(MediaGalleriesPlatformAppBrowserTest,
                        MAYBE_MediaGalleriesNoAccess) {
-  MakeSingleFakeGallery(NULL);
+  MakeSingleFakeGallery();
 
   base::ListValue custom_args;
   custom_args.AppendInteger(num_galleries() + 1);
@@ -451,7 +448,7 @@ IN_PROC_BROWSER_TEST_F(MediaGalleriesPlatformAppBrowserTest,
 IN_PROC_BROWSER_TEST_F(MediaGalleriesPlatformAppBrowserTest,
                        MediaGalleriesRead) {
   RemoveAllGalleries();
-  MakeSingleFakeGallery(NULL);
+  MakeSingleFakeGallery();
   base::ListValue custom_args;
   custom_args.AppendInteger(test_jpg_size());
 
@@ -469,13 +466,13 @@ IN_PROC_BROWSER_TEST_F(MediaGalleriesPlatformAppBrowserTest,
 IN_PROC_BROWSER_TEST_F(MediaGalleriesPlatformAppBrowserTest,
                        MAYBE_MediaGalleriesCopyTo) {
   RemoveAllGalleries();
-  MakeSingleFakeGallery(NULL);
+  MakeSingleFakeGallery();
   ASSERT_TRUE(RunMediaGalleriesTest("copy_to_access")) << message_;
 }
 
 IN_PROC_BROWSER_TEST_F(MediaGalleriesPlatformAppBrowserTest,
                        MediaGalleriesDelete) {
-  MakeSingleFakeGallery(NULL);
+  MakeSingleFakeGallery();
   base::ListValue custom_args;
   custom_args.AppendInteger(num_galleries() + 1);
   ASSERT_TRUE(RunMediaGalleriesTestWithArg("delete_access", custom_args))
@@ -587,22 +584,9 @@ IN_PROC_BROWSER_TEST_F(MediaGalleriesPlatformAppBrowserTest, MAYBE_Scan) {
   ASSERT_TRUE(RunMediaGalleriesTest("scan")) << message_;
 }
 
-IN_PROC_BROWSER_TEST_F(MediaGalleriesPlatformAppBrowserTest, ToURL) {
-  RemoveAllGalleries();
-  MediaGalleryPrefId pref_id;
-  MakeSingleFakeGallery(&pref_id);
-
-  base::ListValue custom_args;
-  custom_args.AppendInteger(base::checked_cast<int>(pref_id));
-  custom_args.AppendString(
-      browser()->profile()->GetPath().BaseName().MaybeAsASCII());
-
-  ASSERT_TRUE(RunMediaGalleriesTestWithArg("tourl", custom_args)) << message_;
-}
-
 IN_PROC_BROWSER_TEST_F(MediaGalleriesPlatformAppBrowserTest, GetMetadata) {
   RemoveAllGalleries();
-  MakeSingleFakeGallery(NULL);
+  MakeSingleFakeGallery();
 
   AddFileToSingleFakeGallery(media::GetTestDataFilePath("90rotation.mp4"));
   AddFileToSingleFakeGallery(media::GetTestDataFilePath("id3_png_test.mp3"));
diff --git a/chrome/browser/media_galleries/fileapi/device_media_async_file_util.cc b/chrome/browser/media_galleries/fileapi/device_media_async_file_util.cc
index f04a5c9..da66f2e 100644
--- a/chrome/browser/media_galleries/fileapi/device_media_async_file_util.cc
+++ b/chrome/browser/media_galleries/fileapi/device_media_async_file_util.cc
@@ -49,13 +49,13 @@ void CreateSnapshotFileOnBlockingPool(
     const base::FilePath& profile_path,
     base::FilePath* snapshot_file_path) {
   DCHECK(snapshot_file_path);
-  base::FilePath media_file_system_dir_path =
+  base::FilePath isolated_media_file_system_dir_path =
       profile_path.AppendASCII(kDeviceMediaAsyncFileUtilTempDir);
-  if (!base::CreateDirectory(media_file_system_dir_path) ||
-      !base::CreateTemporaryFileInDir(media_file_system_dir_path,
+  if (!base::CreateDirectory(isolated_media_file_system_dir_path) ||
+      !base::CreateTemporaryFileInDir(isolated_media_file_system_dir_path,
                                       snapshot_file_path)) {
     LOG(WARNING) << "Could not create media snapshot file "
-                 << media_file_system_dir_path.value();
+                 << isolated_media_file_system_dir_path.value();
     *snapshot_file_path = base::FilePath();
   }
 }
diff --git a/chrome/browser/media_galleries/fileapi/iphoto_file_util.cc b/chrome/browser/media_galleries/fileapi/iphoto_file_util.cc
index e54c3bb..9e07b6e0 100644
--- a/chrome/browser/media_galleries/fileapi/iphoto_file_util.cc
+++ b/chrome/browser/media_galleries/fileapi/iphoto_file_util.cc
@@ -47,21 +47,6 @@ bool ContainsElement(const std::vector<T>& collection, const T& key) {
   return false;
 }
 
-std::vector<std::string> GetVirtualPathComponents(
-    const fileapi::FileSystemURL& url) {
-  ImportedMediaGalleryRegistry* imported_registry =
-      ImportedMediaGalleryRegistry::GetInstance();
-  base::FilePath root = imported_registry->ImportedRoot().AppendASCII("iphoto");
-
-  DCHECK(root.IsParent(url.path()) || root == url.path());
-  base::FilePath virtual_path;
-  root.AppendRelativePath(url.path(), &virtual_path);
-
-  std::vector<std::string> result;
-  fileapi::VirtualPath::GetComponentsUTF8Unsafe(virtual_path, &result);
-  return result;
-}
-
 }  // namespace
 
 const char kIPhotoAlbumsDir[] = "Albums";
@@ -193,7 +178,8 @@ base::File::Error IPhotoFileUtil::GetFileInfoSync(
     const fileapi::FileSystemURL& url,
     base::File::Info* file_info,
     base::FilePath* platform_path) {
-  std::vector<std::string> components = GetVirtualPathComponents(url);
+  std::vector<std::string> components;
+  fileapi::VirtualPath::GetComponentsUTF8Unsafe(url.path(), &components);
 
   if (components.size() == 0) {
     return MakeDirectoryFileInfo(file_info);
@@ -242,7 +228,8 @@ base::File::Error IPhotoFileUtil::ReadDirectorySync(
     const fileapi::FileSystemURL& url,
     EntryList* file_list) {
   DCHECK(file_list->empty());
-  std::vector<std::string> components = GetVirtualPathComponents(url);
+  std::vector<std::string> components;
+  fileapi::VirtualPath::GetComponentsUTF8Unsafe(url.path(), &components);
 
   // Root directory. Child is the /Albums dir.
   if (components.size() == 0) {
@@ -325,7 +312,8 @@ base::File::Error IPhotoFileUtil::GetLocalFilePath(
     fileapi::FileSystemOperationContext* context,
     const fileapi::FileSystemURL& url,
     base::FilePath* local_file_path) {
-  std::vector<std::string> components = GetVirtualPathComponents(url);
+  std::vector<std::string> components;
+  fileapi::VirtualPath::GetComponentsUTF8Unsafe(url.path(), &components);
 
   if (components.size() == 3 && components[0] == kIPhotoAlbumsDir) {
     base::FilePath location = GetDataProvider()->GetPhotoLocationInAlbum(
diff --git a/chrome/browser/media_galleries/fileapi/iphoto_file_util_unittest.cc b/chrome/browser/media_galleries/fileapi/iphoto_file_util_unittest.cc
index 9ffcceb..645beaf 100644
--- a/chrome/browser/media_galleries/fileapi/iphoto_file_util_unittest.cc
+++ b/chrome/browser/media_galleries/fileapi/iphoto_file_util_unittest.cc
@@ -18,7 +18,6 @@
 #include "chrome/browser/media_galleries/fileapi/iphoto_file_util.h"
 #include "chrome/browser/media_galleries/fileapi/media_file_system_backend.h"
 #include "chrome/browser/media_galleries/fileapi/media_path_filter.h"
-#include "chrome/browser/media_galleries/imported_media_gallery_registry.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/test/test_browser_thread.h"
 #include "content/public/test/test_file_system_options.h"
@@ -186,7 +185,6 @@ class IPhotoFileUtilTest : public testing::Test {
 
   virtual void SetUp() OVERRIDE {
     ASSERT_TRUE(profile_dir_.CreateUniqueTempDir());
-    ImportedMediaGalleryRegistry::GetInstance()->Initialize();
 
     scoped_refptr<quota::SpecialStoragePolicy> storage_policy =
         new quota::MockSpecialStoragePolicy();
@@ -231,14 +229,10 @@ class IPhotoFileUtilTest : public testing::Test {
     ASSERT_FALSE(completed);
   }
 
-  FileSystemURL CreateURL(const std::string& path) const {
-    base::FilePath virtual_path =
-        ImportedMediaGalleryRegistry::GetInstance()->ImportedRoot();
-    virtual_path = virtual_path.AppendASCII("iphoto");
-    virtual_path = virtual_path.AppendASCII(path);
+  FileSystemURL CreateURL(const std::string& virtual_path) const {
     return file_system_context_->CreateCrackedFileSystemURL(
         GURL("http://www.example.com"), fileapi::kFileSystemTypeIphoto,
-        virtual_path);
+        base::FilePath::FromUTF8Unsafe(virtual_path));
   }
 
   fileapi::FileSystemOperationRunner* operation_runner() const {
diff --git a/chrome/browser/media_galleries/fileapi/itunes_file_util.cc b/chrome/browser/media_galleries/fileapi/itunes_file_util.cc
index 27c94a1..466aa19 100644
--- a/chrome/browser/media_galleries/fileapi/itunes_file_util.cc
+++ b/chrome/browser/media_galleries/fileapi/itunes_file_util.cc
@@ -34,21 +34,6 @@ base::File::Error MakeDirectoryFileInfo(base::File::Info* file_info) {
   return base::File::FILE_OK;
 }
 
-std::vector<std::string> GetVirtualPathComponents(
-    const fileapi::FileSystemURL& url) {
-  ImportedMediaGalleryRegistry* imported_registry =
-      ImportedMediaGalleryRegistry::GetInstance();
-  base::FilePath root = imported_registry->ImportedRoot().AppendASCII("itunes");
-
-  DCHECK(root.IsParent(url.path()) || root == url.path());
-  base::FilePath virtual_path;
-  root.AppendRelativePath(url.path(), &virtual_path);
-
-  std::vector<std::string> result;
-  fileapi::VirtualPath::GetComponentsUTF8Unsafe(virtual_path, &result);
-  return result;
-}
-
 }  // namespace
 
 const char kITunesLibraryXML[] = "iTunes Music Library.xml";
@@ -128,7 +113,8 @@ base::File::Error ITunesFileUtil::GetFileInfoSync(
     const fileapi::FileSystemURL& url,
     base::File::Info* file_info,
     base::FilePath* platform_path) {
-  std::vector<std::string> components = GetVirtualPathComponents(url);
+  std::vector<std::string> components;
+  fileapi::VirtualPath::GetComponentsUTF8Unsafe(url.path(), &components);
 
   if (components.size() == 0)
     return MakeDirectoryFileInfo(file_info);
@@ -189,7 +175,8 @@ base::File::Error ITunesFileUtil::ReadDirectorySync(
     const fileapi::FileSystemURL& url,
     EntryList* file_list) {
   DCHECK(file_list->empty());
-  std::vector<std::string> components = GetVirtualPathComponents(url);
+  std::vector<std::string> components;
+  fileapi::VirtualPath::GetComponentsUTF8Unsafe(url.path(), &components);
 
   if (components.size() == 0) {
     base::File::Info xml_info;
@@ -299,8 +286,8 @@ base::File::Error ITunesFileUtil::CreateSnapshotFileSync(
     base::File::Info* file_info,
     base::FilePath* platform_path,
     scoped_refptr<webkit_blob::ShareableFileReference>* file_ref) {
-  std::vector<std::string> components = GetVirtualPathComponents(url);
-  if (components.size() != 1 || components[0] != kITunesLibraryXML) {
+  DCHECK(!url.path().IsAbsolute());
+  if (url.path() != base::FilePath().AppendASCII(kITunesLibraryXML)) {
     return NativeMediaFileUtil::CreateSnapshotFileSync(context, url, file_info,
                                                        platform_path, file_ref);
   }
@@ -319,7 +306,8 @@ base::File::Error ITunesFileUtil::GetLocalFilePath(
     fileapi::FileSystemOperationContext* context,
     const fileapi::FileSystemURL& url,
     base::FilePath* local_file_path) {
-  std::vector<std::string> components = GetVirtualPathComponents(url);
+  std::vector<std::string> components;
+  fileapi::VirtualPath::GetComponentsUTF8Unsafe(url.path(), &components);
 
   if (components.size() == 1 && components[0] == kITunesLibraryXML) {
     *local_file_path = GetDataProvider()->library_path();
diff --git a/chrome/browser/media_galleries/fileapi/itunes_file_util_unittest.cc b/chrome/browser/media_galleries/fileapi/itunes_file_util_unittest.cc
index 11b5973..43a09be 100644
--- a/chrome/browser/media_galleries/fileapi/itunes_file_util_unittest.cc
+++ b/chrome/browser/media_galleries/fileapi/itunes_file_util_unittest.cc
@@ -17,7 +17,6 @@
 #include "chrome/browser/media_galleries/fileapi/itunes_file_util.h"
 #include "chrome/browser/media_galleries/fileapi/media_file_system_backend.h"
 #include "chrome/browser/media_galleries/fileapi/media_path_filter.h"
-#include "chrome/browser/media_galleries/imported_media_gallery_registry.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/test/test_browser_thread.h"
 #include "content/public/test/test_file_system_options.h"
@@ -154,7 +153,6 @@ class ItunesFileUtilTest : public testing::Test {
 
   virtual void SetUp() OVERRIDE {
     ASSERT_TRUE(profile_dir_.CreateUniqueTempDir());
-    ImportedMediaGalleryRegistry::GetInstance()->Initialize();
 
     scoped_refptr<quota::SpecialStoragePolicy> storage_policy =
         new quota::MockSpecialStoragePolicy();
@@ -199,14 +197,10 @@ class ItunesFileUtilTest : public testing::Test {
     ASSERT_FALSE(completed);
   }
 
-  FileSystemURL CreateURL(const std::string& path) const {
-    base::FilePath virtual_path =
-        ImportedMediaGalleryRegistry::GetInstance()->ImportedRoot();
-    virtual_path = virtual_path.AppendASCII("itunes");
-    virtual_path = virtual_path.AppendASCII(path);
+  FileSystemURL CreateURL(const std::string& virtual_path) const {
     return file_system_context_->CreateCrackedFileSystemURL(
         GURL("http://www.example.com"), fileapi::kFileSystemTypeItunes,
-        virtual_path);
+        base::FilePath::FromUTF8Unsafe(virtual_path));
   }
 
   fileapi::FileSystemOperationRunner* operation_runner() const {
diff --git a/chrome/browser/media_galleries/fileapi/media_file_system_backend.cc b/chrome/browser/media_galleries/fileapi/media_file_system_backend.cc
index 3be12a7..eab10d4 100644
--- a/chrome/browser/media_galleries/fileapi/media_file_system_backend.cc
+++ b/chrome/browser/media_galleries/fileapi/media_file_system_backend.cc
@@ -12,31 +12,19 @@
 #include "base/message_loop/message_loop_proxy.h"
 #include "base/platform_file.h"
 #include "base/sequenced_task_runner.h"
-#include "base/strings/string_number_conversions.h"
-#include "base/strings/string_util.h"
-#include "base/strings/utf_string_conversions.h"
 #include "base/threading/sequenced_worker_pool.h"
-#include "chrome/browser/browser_process.h"
-#include "chrome/browser/extensions/extension_service.h"
 #include "chrome/browser/media_galleries/fileapi/device_media_async_file_util.h"
 #include "chrome/browser/media_galleries/fileapi/media_file_validator_factory.h"
 #include "chrome/browser/media_galleries/fileapi/media_path_filter.h"
 #include "chrome/browser/media_galleries/fileapi/native_media_file_util.h"
-#include "chrome/browser/media_galleries/media_file_system_registry.h"
-#include "chrome/browser/profiles/profile.h"
 #include "content/public/browser/browser_thread.h"
-#include "content/public/browser/render_process_host.h"
-#include "content/public/browser/render_view_host.h"
-#include "content/public/browser/resource_request_info.h"
-#include "extensions/browser/extension_system.h"
-#include "net/url_request/url_request.h"
 #include "webkit/browser/blob/file_stream_reader.h"
 #include "webkit/browser/fileapi/copy_or_move_file_validator.h"
 #include "webkit/browser/fileapi/file_stream_writer.h"
 #include "webkit/browser/fileapi/file_system_context.h"
 #include "webkit/browser/fileapi/file_system_operation.h"
 #include "webkit/browser/fileapi/file_system_operation_context.h"
-#include "webkit/browser/fileapi/file_system_url.h"
+#include "webkit/browser/fileapi/isolated_context.h"
 #include "webkit/browser/fileapi/native_file_util.h"
 #include "webkit/common/fileapi/file_system_types.h"
 #include "webkit/common/fileapi/file_system_util.h"
@@ -53,67 +41,6 @@
 using fileapi::FileSystemContext;
 using fileapi::FileSystemURL;
 
-namespace {
-
-const char kMediaGalleryMountPrefix[] = "media_galleries-";
-
-void OnPreferencesInit(
-    const content::RenderViewHost* rvh,
-    const extensions::Extension* extension,
-    MediaGalleryPrefId pref_id,
-    const base::Callback<void(base::File::Error result)>& callback) {
-  MediaFileSystemRegistry* registry =
-      g_browser_process->media_file_system_registry();
-  registry->RegisterMediaFileSystemForExtension(rvh, extension, pref_id,
-                                                callback);
-}
-
-void AttemptAutoMountOnUIThread(
-    int32 process_id,
-    int32 routing_id,
-    const std::string& storage_domain,
-    const std::string& mount_point,
-    const base::Callback<void(base::File::Error result)>& callback) {
-  DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
-
-  content::RenderViewHost* rvh =
-      content::RenderViewHost::FromID(process_id, routing_id);
-  if (rvh) {
-    Profile* profile =
-        Profile::FromBrowserContext(rvh->GetProcess()->GetBrowserContext());
-
-    ExtensionService* extension_service =
-        extensions::ExtensionSystem::Get(profile)->extension_service();
-    const extensions::Extension* extension =
-        extension_service->GetExtensionById(storage_domain,
-                                            false /*include disabled*/);
-    std::string expected_mount_prefix =
-        MediaFileSystemBackend::ConstructMountName(
-            profile->GetPath(), storage_domain, kInvalidMediaGalleryPrefId);
-    MediaGalleryPrefId pref_id = kInvalidMediaGalleryPrefId;
-    if (extension &&
-        extension->id() == storage_domain &&
-        StartsWithASCII(mount_point, expected_mount_prefix, true) &&
-        base::StringToUint64(mount_point.substr(expected_mount_prefix.size()),
-                             &pref_id) &&
-        pref_id != kInvalidMediaGalleryPrefId) {
-      MediaGalleriesPreferences* preferences =
-          g_browser_process->media_file_system_registry()->GetPreferences(
-              profile);
-      preferences->EnsureInitialized(
-          base::Bind(&OnPreferencesInit, rvh, extension, pref_id, callback));
-      return;
-    }
-  }
-
-  content::BrowserThread::PostTask(
-      content::BrowserThread::IO,
-      FROM_HERE,
-      base::Bind(callback, base::File::FILE_ERROR_NOT_FOUND));
-}
-
-}  // namespace
-
 const char MediaFileSystemBackend::kMediaTaskRunnerName[] =
     "media-task-runner";
 
@@ -160,59 +87,6 @@ MediaFileSystemBackend::MediaTaskRunner() {
   return pool->GetSequencedTaskRunner(media_sequence_token);
 }
 
-// static
-std::string MediaFileSystemBackend::ConstructMountName(
-    const base::FilePath& profile_path,
-    const std::string& extension_id,
-    MediaGalleryPrefId pref_id) {
-  std::string name(kMediaGalleryMountPrefix);
-  name.append(profile_path.BaseName().MaybeAsASCII());
-  name.append("-");
-  name.append(extension_id);
-  name.append("-");
-  if (pref_id != kInvalidMediaGalleryPrefId)
-    name.append(base::Uint64ToString(pref_id));
-  base::ReplaceChars(name, " /", "_", &name);
-  return name;
-}
-
-// static
-bool MediaFileSystemBackend::AttemptAutoMountForURLRequest(
-    const net::URLRequest* url_request,
-    const fileapi::FileSystemURL& filesystem_url,
-    const std::string& storage_domain,
-    const base::Callback<void(base::File::Error result)>& callback) {
-  if (storage_domain.empty() ||
-      filesystem_url.type() != fileapi::kFileSystemTypeExternal ||
-      storage_domain != filesystem_url.origin().host()) {
-    return false;
-  }
-
-  const base::FilePath& virtual_path = filesystem_url.path();
-  if (virtual_path.ReferencesParent())
-    return false;
-  std::vector<base::FilePath::StringType> components;
-  virtual_path.GetComponents(&components);
-  if (components.empty())
-    return false;
-  std::string mount_point = base::FilePath(components[0]).AsUTF8Unsafe();
-  if (!StartsWithASCII(mount_point, kMediaGalleryMountPrefix, true))
-    return false;
-
-  const content::ResourceRequestInfo* request_info =
-      content::ResourceRequestInfo::ForRequest(url_request);
-  if (!request_info)
-    return false;
-
-  content::BrowserThread::PostTask(
-      content::BrowserThread::UI,
-      FROM_HERE,
-      base::Bind(&AttemptAutoMountOnUIThread, request_info->GetChildID(),
-                 request_info->GetRouteID(), storage_domain, mount_point,
-                 callback));
-  return true;
-}
-
 bool MediaFileSystemBackend::CanHandleType(
     fileapi::FileSystemType type) const {
   switch (type) {
@@ -238,7 +112,7 @@ void MediaFileSystemBackend::ResolveURL(
     const FileSystemURL& url,
     fileapi::OpenFileSystemMode mode,
     const OpenFileSystemCallback& callback) {
-  // We never allow opening a new FileSystem via usual ResolveURL.
+  // We never allow opening a new isolated FileSystem via usual ResolveURL.
   base::MessageLoopProxy::current()->PostTask(
       FROM_HERE,
       base::Bind(callback,
diff --git a/chrome/browser/media_galleries/fileapi/media_file_system_backend.h b/chrome/browser/media_galleries/fileapi/media_file_system_backend.h
index c5b7991..7dbfbd1 100644
--- a/chrome/browser/media_galleries/fileapi/media_file_system_backend.h
+++ b/chrome/browser/media_galleries/fileapi/media_file_system_backend.h
@@ -5,28 +5,20 @@
 #ifndef CHROME_BROWSER_MEDIA_GALLERIES_FILEAPI_MEDIA_FILE_SYSTEM_BACKEND_H_
 #define CHROME_BROWSER_MEDIA_GALLERIES_FILEAPI_MEDIA_FILE_SYSTEM_BACKEND_H_
 
-#include <string>
-
-#include "base/callback.h"
-#include "base/files/file_path.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
-#include "chrome/browser/media_galleries/media_galleries_preferences.h"
 #include "webkit/browser/fileapi/file_system_backend.h"
 
 namespace base {
 class SequencedTaskRunner;
 }
 
-namespace fileapi {
-class FileSystemURL;
-}
-
 namespace net {
 class URLRequest;
 }
 
 class MediaPathFilter;
+
 class DeviceMediaAsyncFileUtil;
 
 class MediaFileSystemBackend : public fileapi::FileSystemBackend {
@@ -41,12 +33,6 @@ class MediaFileSystemBackend : public fileapi::FileSystemBackend {
   static bool CurrentlyOnMediaTaskRunnerThread();
   static scoped_refptr<base::SequencedTaskRunner> MediaTaskRunner();
 
-  // Construct the mount point for the gallery specified by |pref_id| in
-  // the profile located in |profile_path|.
-  static std::string ConstructMountName(const base::FilePath& profile_path,
-                                        const std::string& extension_id,
-                                        MediaGalleryPrefId pref_id);
-
   static bool AttemptAutoMountForURLRequest(
       const net::URLRequest* url_request,
       const fileapi::FileSystemURL& filesystem_url,
diff --git a/chrome/browser/media_galleries/fileapi/mtp_device_async_delegate.h b/chrome/browser/media_galleries/fileapi/mtp_device_async_delegate.h
index e28c9a6..a6cfebf 100644
--- a/chrome/browser/media_galleries/fileapi/mtp_device_async_delegate.h
+++ b/chrome/browser/media_galleries/fileapi/mtp_device_async_delegate.h
@@ -19,7 +19,7 @@ class IOBuffer;
 }
 
 // Asynchronous delegate for media transfer protocol (MTP) device to perform
-// media device file system operations. Class that implements this
+// media device isolated file system operations. Class that implements this
 // delegate does the actual communication with the MTP device.
 // The lifetime of the delegate is managed by the MTPDeviceMapService class.
 // Member functions and callbacks run on the IO thread.
diff --git a/chrome/browser/media_galleries/fileapi/mtp_device_map_service.cc b/chrome/browser/media_galleries/fileapi/mtp_device_map_service.cc
index 295c019..69d8d07 100644
--- a/chrome/browser/media_galleries/fileapi/mtp_device_map_service.cc
+++ b/chrome/browser/media_galleries/fileapi/mtp_device_map_service.cc
@@ -10,7 +10,7 @@
 #include "base/stl_util.h"
 #include "chrome/browser/media_galleries/fileapi/mtp_device_async_delegate.h"
 #include "content/public/browser/browser_thread.h"
-#include "webkit/browser/fileapi/external_mount_points.h"
+#include "webkit/browser/fileapi/isolated_context.h"
 
 namespace {
 
@@ -85,7 +85,7 @@ MTPDeviceAsyncDelegate* MTPDeviceMapService::GetMTPDeviceAsyncDelegate(
     const std::string& filesystem_id) {
   DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::IO));
   base::FilePath device_path;
-  if (!fileapi::ExternalMountPoints::GetSystemInstance()->GetRegisteredPath(
+  if (!fileapi::IsolatedContext::GetInstance()->GetRegisteredPath(
           filesystem_id, &device_path)) {
     return NULL;
   }
diff --git a/chrome/browser/media_galleries/fileapi/picasa_file_util.cc b/chrome/browser/media_galleries/fileapi/picasa_file_util.cc
index 2965b9b..f9a5ba8 100644
--- a/chrome/browser/media_galleries/fileapi/picasa_file_util.cc
+++ b/chrome/browser/media_galleries/fileapi/picasa_file_util.cc
@@ -49,24 +49,11 @@ base::File::Error FindAlbumInfo(const std::string& key,
   return base::File::FILE_OK;
 }
 
-std::vector<std::string> GetVirtualPathComponents(
-    const fileapi::FileSystemURL& url) {
-  ImportedMediaGalleryRegistry* imported_registry =
-      ImportedMediaGalleryRegistry::GetInstance();
-  base::FilePath root = imported_registry->ImportedRoot().AppendASCII("picasa");
-
-  DCHECK(root.IsParent(url.path()) || root == url.path());
-  base::FilePath virtual_path;
-  root.AppendRelativePath(url.path(), &virtual_path);
-
-  std::vector<std::string> result;
-  fileapi::VirtualPath::GetComponentsUTF8Unsafe(virtual_path, &result);
-  return result;
-}
-
 PicasaDataProvider::DataType GetDataTypeForURL(
     const fileapi::FileSystemURL& url) {
-  std::vector<std::string> components = GetVirtualPathComponents(url);
+  std::vector<std::string> components;
+  fileapi::VirtualPath::GetComponentsUTF8Unsafe(url.path(), &components);
+
   if (components.size() >= 2 && components[0] == kPicasaDirAlbums)
     return PicasaDataProvider::ALBUMS_IMAGES_DATA;
 
@@ -134,7 +121,8 @@ base::File::Error PicasaFileUtil::GetFileInfoSync(
   if (platform_path)
     *platform_path = base::FilePath();
 
-  std::vector<std::string> components = GetVirtualPathComponents(url);
+  std::vector<std::string> components;
+  fileapi::VirtualPath::GetComponentsUTF8Unsafe(url.path(), &components);
 
   switch (components.size()) {
     case 0:
@@ -202,7 +190,9 @@ base::File::Error PicasaFileUtil::ReadDirectorySync(
   if (!file_info.is_directory)
     return base::File::FILE_ERROR_NOT_A_DIRECTORY;
 
-  std::vector<std::string> components = GetVirtualPathComponents(url);
+  std::vector<std::string> components;
+  fileapi::VirtualPath::GetComponentsUTF8Unsafe(url.path(), &components);
+
   switch (components.size()) {
     case 0: {
       // Root directory.
@@ -307,7 +297,8 @@ base::File::Error PicasaFileUtil::GetLocalFilePath(
     base::FilePath* local_file_path) {
   DCHECK(local_file_path);
   DCHECK(url.is_valid());
-  std::vector<std::string> components = GetVirtualPathComponents(url);
+  std::vector<std::string> components;
+  fileapi::VirtualPath::GetComponentsUTF8Unsafe(url.path(), &components);
 
   switch (components.size()) {
     case 2:
diff --git a/chrome/browser/media_galleries/fileapi/picasa_file_util_unittest.cc b/chrome/browser/media_galleries/fileapi/picasa_file_util_unittest.cc
index edd294c..c70c2ca 100644
--- a/chrome/browser/media_galleries/fileapi/picasa_file_util_unittest.cc
+++ b/chrome/browser/media_galleries/fileapi/picasa_file_util_unittest.cc
@@ -22,7 +22,6 @@
 #include "chrome/browser/media_galleries/fileapi/media_path_filter.h"
 #include "chrome/browser/media_galleries/fileapi/picasa_data_provider.h"
 #include "chrome/browser/media_galleries/fileapi/picasa_file_util.h"
-#include "chrome/browser/media_galleries/imported_media_gallery_registry.h"
 #include "chrome/common/media_galleries/picasa_types.h"
 #include "chrome/common/media_galleries/pmp_constants.h"
 #include "content/public/browser/browser_thread.h"
@@ -229,7 +228,6 @@ class PicasaFileUtilTest : public testing::Test {
 
   virtual void SetUp() OVERRIDE {
     ASSERT_TRUE(profile_dir_.CreateUniqueTempDir());
-    ImportedMediaGalleryRegistry::GetInstance()->Initialize();
 
     scoped_refptr<quota::SpecialStoragePolicy> storage_policy =
         new quota::MockSpecialStoragePolicy();
@@ -358,14 +356,10 @@ class PicasaFileUtilTest : public testing::Test {
     EXPECT_EQ(0u, contents.size());
   }
 
-  FileSystemURL CreateURL(const std::string& path) const {
-    base::FilePath virtual_path =
-        ImportedMediaGalleryRegistry::GetInstance()->ImportedRoot();
-    virtual_path = virtual_path.AppendASCII("picasa");
-    virtual_path = virtual_path.AppendASCII(path);
+  FileSystemURL CreateURL(const std::string& virtual_path) const {
     return file_system_context_->CreateCrackedFileSystemURL(
         GURL("http://www.example.com"), fileapi::kFileSystemTypePicasa,
-        virtual_path);
+        base::FilePath::FromUTF8Unsafe(virtual_path));
   }
 
   fileapi::FileSystemOperationRunner* operation_runner() const {
diff --git a/chrome/browser/media_galleries/imported_media_gallery_registry.cc b/chrome/browser/media_galleries/imported_media_gallery_registry.cc
index 506b8c9..245d051 100644
--- a/chrome/browser/media_galleries/imported_media_gallery_registry.cc
+++ b/chrome/browser/media_galleries/imported_media_gallery_registry.cc
@@ -5,7 +5,6 @@
 #include "chrome/browser/media_galleries/imported_media_gallery_registry.h"
 
 #include "base/bind.h"
-#include "base/file_util.h"
 #include "base/logging.h"
 #include "chrome/browser/media_galleries/fileapi/iphoto_data_provider.h"
 #include "chrome/browser/media_galleries/fileapi/itunes_data_provider.h"
@@ -13,11 +12,10 @@
 #include "chrome/browser/media_galleries/fileapi/picasa_data_provider.h"
 #include "chrome/common/extensions/extension_constants.h"
 #include "content/public/browser/browser_thread.h"
-#include "webkit/browser/fileapi/external_mount_points.h"
-#include "webkit/common/fileapi/file_system_mount_option.h"
+#include "webkit/browser/fileapi/isolated_context.h"
 
 using base::Bind;
-using fileapi::ExternalMountPoints;
+using fileapi::IsolatedContext;
 
 namespace {
 
@@ -31,38 +29,25 @@ ImportedMediaGalleryRegistry* ImportedMediaGalleryRegistry::GetInstance() {
   return g_imported_media_gallery_registry.Pointer();
 }
 
-void ImportedMediaGalleryRegistry::Initialize() {
-  base::ThreadRestrictions::AssertIOAllowed();
-  if (imported_root_.empty()) {
-    if (!base::CreateTemporaryFile(&imported_root_))
-      imported_root_ = base::FilePath();
-    // TODO(vandebo) Setting the permissions of |imported_root_| in CPSP to
-    // zero would be an extra step to ensure permissions are correctly
-    // enforced.
-  }
-}
-
-bool ImportedMediaGalleryRegistry::RegisterPicasaFilesystemOnUIThread(
-    const std::string& fs_name, const base::FilePath& database_path) {
+std::string ImportedMediaGalleryRegistry::RegisterPicasaFilesystemOnUIThread(
+    const base::FilePath& database_path) {
   DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
-  DCHECK(!fs_name.empty());
   DCHECK(!database_path.empty());
 
-  bool result = false;
+  std::string fsid;
 
 #if defined(OS_WIN) || defined(OS_MACOSX)
-  base::FilePath root = ImportedRoot();
-  if (root.empty())
-    return false;
-  result = ExternalMountPoints::GetSystemInstance()->RegisterFileSystem(
-      fs_name, fileapi::kFileSystemTypePicasa, fileapi::FileSystemMountOption(),
-      root.AppendASCII("picasa"));
-  if (!result)
-    return result;
-
-  picasa_fs_names_.insert(fs_name);
-
-  if (picasa_fs_names_.size() == 1) {
+  fsid = IsolatedContext::GetInstance()->RegisterFileSystemForVirtualPath(
+           fileapi::kFileSystemTypePicasa,
+           extension_misc::kMediaFileSystemPathPart,
+           base::FilePath());
+
+  if (fsid.empty())
+    return fsid;
+
+  picasa_fsids_.insert(fsid);
+
+  if (picasa_fsids_.size() == 1) {
     MediaFileSystemBackend::MediaTaskRunner()->PostTask(
         FROM_HERE,
         Bind(&ImportedMediaGalleryRegistry::RegisterPicasaFileSystem,
@@ -75,29 +60,28 @@ bool ImportedMediaGalleryRegistry::RegisterPicasaFilesystemOnUIThread(
   }
 #endif  // defined(OS_WIN) || defined(OS_MACOSX)
 
-  return result;
+  return fsid;
 }
 
-bool ImportedMediaGalleryRegistry::RegisterITunesFilesystemOnUIThread(
-    const std::string& fs_name, const base::FilePath& library_xml_path) {
+std::string ImportedMediaGalleryRegistry::RegisterITunesFilesystemOnUIThread(
+    const base::FilePath& library_xml_path) {
   DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
   DCHECK(!library_xml_path.empty());
 
-  bool result = false;
+  std::string fsid;
 
 #if defined(OS_WIN) || defined(OS_MACOSX)
-  base::FilePath root = ImportedRoot();
-  if (root.empty())
-    return false;
-  result = ExternalMountPoints::GetSystemInstance()->RegisterFileSystem(
-      fs_name, fileapi::kFileSystemTypeItunes, fileapi::FileSystemMountOption(),
-      root.AppendASCII("itunes"));
-  if (!result)
-    return result;
-
-  itunes_fs_names_.insert(fs_name);
-
-  if (itunes_fs_names_.size() == 1) {
+  fsid = IsolatedContext::GetInstance()->RegisterFileSystemForVirtualPath(
+           fileapi::kFileSystemTypeItunes,
+           extension_misc::kMediaFileSystemPathPart,
+           base::FilePath());
+
+  if (fsid.empty())
+    return fsid;
+
+  itunes_fsids_.insert(fsid);
+
+  if (itunes_fsids_.size() == 1) {
     MediaFileSystemBackend::MediaTaskRunner()->PostTask(
         FROM_HERE,
         Bind(&ImportedMediaGalleryRegistry::RegisterITunesFileSystem,
@@ -110,31 +94,30 @@ bool ImportedMediaGalleryRegistry::RegisterITunesFilesystemOnUIThread(
   }
 #endif  // defined(OS_WIN) || defined(OS_MACOSX)
 
-  return result;
+  return fsid;
 }
 
-bool ImportedMediaGalleryRegistry::RegisterIPhotoFilesystemOnUIThread(
-    const std::string& fs_name, const base::FilePath& library_xml_path) {
+std::string ImportedMediaGalleryRegistry::RegisterIPhotoFilesystemOnUIThread(
+    const base::FilePath& library_xml_path) {
   DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
   DCHECK(!library_xml_path.empty());
 
-  bool result = false;
+  std::string fsid;
 
   // TODO(gbillock): Investigate how to refactor this to reduce duplicated
   // code.
 #if defined(OS_MACOSX)
-  base::FilePath root = ImportedRoot();
-  if (root.empty())
-    return false;
-  result = ExternalMountPoints::GetSystemInstance()->RegisterFileSystem(
-      fs_name, fileapi::kFileSystemTypeIphoto, fileapi::FileSystemMountOption(),
-      root.AppendASCII("iphoto"));
-  if (!result)
-    return result;
-
-  iphoto_fs_names_.insert(fs_name);
-
-  if (iphoto_fs_names_.size() == 1) {
+  fsid = IsolatedContext::GetInstance()->RegisterFileSystemForVirtualPath(
+           fileapi::kFileSystemTypeIphoto,
+           extension_misc::kMediaFileSystemPathPart,
+           base::FilePath());
+
+  if (fsid.empty())
+    return fsid;
+
+  iphoto_fsids_.insert(fsid);
+
+  if (iphoto_fsids_.size() == 1) {
     MediaFileSystemBackend::MediaTaskRunner()->PostTask(
         FROM_HERE,
         Bind(&ImportedMediaGalleryRegistry::RegisterIPhotoFileSystem,
@@ -147,55 +130,50 @@ bool ImportedMediaGalleryRegistry::RegisterIPhotoFilesystemOnUIThread(
   }
 #endif  // defined(OS_MACOSX)
 
-  return result;
+  return fsid;
 }
 
 bool ImportedMediaGalleryRegistry::RevokeImportedFilesystemOnUIThread(
-    const std::string& fs_name) {
+    const std::string& fsid) {
   DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
 
 #if defined(OS_WIN) || defined(OS_MACOSX)
-  if (picasa_fs_names_.erase(fs_name)) {
-    if (picasa_fs_names_.empty()) {
+  if (picasa_fsids_.erase(fsid)) {
+    if (picasa_fsids_.empty()) {
       MediaFileSystemBackend::MediaTaskRunner()->PostTask(
           FROM_HERE,
           Bind(&ImportedMediaGalleryRegistry::RevokePicasaFileSystem,
                base::Unretained(this)));
     }
-    return ExternalMountPoints::GetSystemInstance()->RevokeFileSystem(fs_name);
+    return IsolatedContext::GetInstance()->RevokeFileSystem(fsid);
   }
 
-  if (itunes_fs_names_.erase(fs_name)) {
-    if (itunes_fs_names_.empty()) {
+  if (itunes_fsids_.erase(fsid)) {
+    if (itunes_fsids_.empty()) {
       MediaFileSystemBackend::MediaTaskRunner()->PostTask(
           FROM_HERE,
           Bind(&ImportedMediaGalleryRegistry::RevokeITunesFileSystem,
                base::Unretained(this)));
     }
-    return ExternalMountPoints::GetSystemInstance()->RevokeFileSystem(fs_name);
+    return IsolatedContext::GetInstance()->RevokeFileSystem(fsid);
   }
 #endif  // defined(OS_WIN) || defined(OS_MACOSX)
 
 #if defined(OS_MACOSX)
-  if (iphoto_fs_names_.erase(fs_name)) {
-    if (iphoto_fs_names_.empty()) {
+  if (iphoto_fsids_.erase(fsid)) {
+    if (iphoto_fsids_.empty()) {
       MediaFileSystemBackend::MediaTaskRunner()->PostTask(
           FROM_HERE,
           Bind(&ImportedMediaGalleryRegistry::RevokeIPhotoFileSystem,
                base::Unretained(this)));
     }
-    return ExternalMountPoints::GetSystemInstance()->RevokeFileSystem(fs_name);
+    return IsolatedContext::GetInstance()->RevokeFileSystem(fsid);
   }
 #endif  // defined(OS_MACOSX)
 
   return false;
 }
 
-base::FilePath ImportedMediaGalleryRegistry::ImportedRoot() {
-  DCHECK(!imported_root_.empty());
-  return imported_root_;
-}
-
 #if defined(OS_WIN) || defined(OS_MACOSX)
 // static
 picasa::PicasaDataProvider*
@@ -227,14 +205,12 @@ ImportedMediaGalleryRegistry::IPhotoDataProvider() {
 ImportedMediaGalleryRegistry::ImportedMediaGalleryRegistry() {}
 
 ImportedMediaGalleryRegistry::~ImportedMediaGalleryRegistry() {
-  if (!imported_root_.empty())
-    base::DeleteFile(imported_root_, false);
 #if defined(OS_WIN) || defined(OS_MACOSX)
-  DCHECK_EQ(0U, picasa_fs_names_.size());
-  DCHECK_EQ(0U, itunes_fs_names_.size());
+  DCHECK_EQ(0U, picasa_fsids_.size());
+  DCHECK_EQ(0U, itunes_fsids_.size());
 #endif  // defined(OS_WIN) || defined(OS_MACOSX)
 #if defined(OS_MACOSX)
-  DCHECK_EQ(0U, iphoto_fs_names_.size());
+  DCHECK_EQ(0U, iphoto_fsids_.size());
 #endif  // defined(OS_MACOSX)
 }
 
diff --git a/chrome/browser/media_galleries/imported_media_gallery_registry.h b/chrome/browser/media_galleries/imported_media_gallery_registry.h
index 8c343c1..9e7e2a2 100644
--- a/chrome/browser/media_galleries/imported_media_gallery_registry.h
+++ b/chrome/browser/media_galleries/imported_media_gallery_registry.h
@@ -37,24 +37,17 @@ class ImportedMediaGalleryRegistry {
  public:
   static ImportedMediaGalleryRegistry* GetInstance();
 
-  void Initialize();
-
   // Should be called on the UI thread only.
-  bool RegisterPicasaFilesystemOnUIThread(const std::string& fs_name,
-                                          const base::FilePath& database_path);
+  std::string RegisterPicasaFilesystemOnUIThread(
+      const base::FilePath& database_path);
 
-  bool RegisterITunesFilesystemOnUIThread(
-      const std::string& fs_name,
+  std::string RegisterITunesFilesystemOnUIThread(
       const base::FilePath& xml_library_path);
 
-  bool RegisterIPhotoFilesystemOnUIThread(
-      const std::string& fs_name,
+  std::string RegisterIPhotoFilesystemOnUIThread(
       const base::FilePath& xml_library_path);
 
-  bool RevokeImportedFilesystemOnUIThread(const std::string& fs_name);
-
-  // Path where all virtual file systems are "mounted."
-  base::FilePath ImportedRoot();
+  bool RevokeImportedFilesystemOnUIThread(const std::string& fsid);
 
   // Should be called on the MediaTaskRunner thread only.
 #if defined(OS_WIN) || defined(OS_MACOSX)
@@ -88,16 +81,14 @@ class ImportedMediaGalleryRegistry {
   void RevokeIPhotoFileSystem();
 #endif  // defined(OS_MACOSX)
 
-  base::FilePath imported_root_;
-
 #if defined(OS_WIN) || defined(OS_MACOSX)
   // The data providers are only set or accessed on the task runner thread.
   scoped_ptr<picasa::PicasaDataProvider> picasa_data_provider_;
   scoped_ptr<itunes::ITunesDataProvider> itunes_data_provider_;
 
   // The remaining members are only accessed on the IO thread.
-  std::set<std::string> picasa_fs_names_;
-  std::set<std::string> itunes_fs_names_;
+  std::set<std::string> picasa_fsids_;
+  std::set<std::string> itunes_fsids_;
 
 #ifndef NDEBUG
   base::FilePath picasa_database_path_;
@@ -108,7 +99,7 @@ class ImportedMediaGalleryRegistry {
 #if defined(OS_MACOSX)
   scoped_ptr<iphoto::IPhotoDataProvider> iphoto_data_provider_;
 
-  std::set<std::string> iphoto_fs_names_;
+  std::set<std::string> iphoto_fsids_;
 
 #ifndef NDEBUG
   base::FilePath iphoto_xml_library_path_;
diff --git a/chrome/browser/media_galleries/media_file_system_context.h b/chrome/browser/media_galleries/media_file_system_context.h
index a430b31..0ecafd6 100644
--- a/chrome/browser/media_galleries/media_file_system_context.h
+++ b/chrome/browser/media_galleries/media_file_system_context.h
@@ -19,18 +19,13 @@ class MediaFileSystemContext {
  public:
   virtual ~MediaFileSystemContext() {}
 
-  // Register a new media file system for |path| as |fs_name|.
-  virtual bool RegisterFileSystem(const std::string& device_id,
-                                  const std::string& fs_name,
-                                  const base::FilePath& path) = 0;
-
-  // Revoke the passed |fs_name|.
-  virtual void RevokeFileSystem(const std::string& fs_name) = 0;
-
-  // Return the mount point root for the given |fs_name|. Returns an empty path
-  // if |fs_name| is not valid.
-  virtual base::FilePath GetRegisteredPath(
-      const std::string& fs_name) const = 0;
+  // Register a new media file system for |path| and return the corresponding
+  // filesystem ID.
+  virtual std::string RegisterFileSystem(
+      const std::string& device_id, const base::FilePath& path) = 0;
+
+  // Revoke the passed |fsid|.
+  virtual void RevokeFileSystem(const std::string& fsid) = 0;
 };
 
 #endif  // CHROME_BROWSER_MEDIA_GALLERIES_MEDIA_FILE_SYSTEM_CONTEXT_H_
diff --git a/chrome/browser/media_galleries/media_file_system_registry.cc b/chrome/browser/media_galleries/media_file_system_registry.cc
index 9451af8..1010eb6 100644
--- a/chrome/browser/media_galleries/media_file_system_registry.cc
+++ b/chrome/browser/media_galleries/media_file_system_registry.cc
@@ -13,7 +13,6 @@
 #include "base/prefs/pref_service.h"
 #include "base/stl_util.h"
 #include "chrome/browser/extensions/extension_service.h"
-#include "chrome/browser/media_galleries/fileapi/media_file_system_backend.h"
 #include "chrome/browser/media_galleries/fileapi/mtp_device_map_service.h"
 #include "chrome/browser/media_galleries/imported_media_gallery_registry.h"
 #include "chrome/browser/media_galleries/media_file_system_context.h"
@@ -37,15 +36,14 @@
 #include "extensions/browser/extension_system.h"
 #include "extensions/common/extension.h"
 #include "extensions/common/extension_set.h"
-#include "webkit/browser/fileapi/external_mount_points.h"
-#include "webkit/common/fileapi/file_system_mount_option.h"
+#include "webkit/browser/fileapi/isolated_context.h"
 #include "webkit/common/fileapi/file_system_types.h"
 
 using content::BrowserThread;
 using content::NavigationController;
 using content::RenderProcessHost;
 using content::WebContents;
-using fileapi::ExternalMountPoints;
+using fileapi::IsolatedContext;
 using storage_monitor::MediaStorageUtil;
 using storage_monitor::StorageInfo;
 using storage_monitor::StorageMonitor;
@@ -263,19 +261,15 @@ class ExtensionGalleriesHost
   // |no_references_callback| is called when the last RenderViewHost reference
   // goes away. RenderViewHost references are added through ReferenceFromRVH().
   ExtensionGalleriesHost(MediaFileSystemContext* file_system_context,
-                         const base::FilePath& profile_path,
-                         const std::string& extension_id,
                          const base::Closure& no_references_callback)
       : file_system_context_(file_system_context),
-        profile_path_(profile_path),
-        extension_id_(extension_id),
         no_references_callback_(no_references_callback),
         rph_refs_(base::Bind(&ExtensionGalleriesHost::CleanUp,
                              base::Unretained(this))) {
   }
 
   // For each gallery in the list of permitted |galleries|, checks if the
-  // device is attached and if so looks up or creates a file system name and
+  // device is attached and if so looks up or creates a file system id and
   // passes the information needed for the renderer to create those file
   // system objects to the |callback|.
   void GetMediaFileSystems(const MediaGalleryPrefIdSet& galleries,
@@ -294,20 +288,6 @@ class ExtensionGalleriesHost
         base::Owned(device_ids), galleries, galleries_info, callback));
   }
 
-  // Checks if |gallery| is attached and if so, registers the file system and
-  // then calls |callback| with the result.
-  void RegisterMediaFileSystem(
-      const MediaGalleryPrefInfo& gallery,
-      const base::Callback<void(base::File::Error result)>& callback) {
-    // Extract all the device ids so we can make sure they are attached.
-    MediaStorageUtil::DeviceIdSet* device_ids =
-        new MediaStorageUtil::DeviceIdSet;
-    device_ids->insert(gallery.device_id);
-    MediaStorageUtil::FilterAttachedDevices(device_ids, base::Bind(
-        &ExtensionGalleriesHost::RegisterAttachedMediaFileSystem, this,
-        base::Owned(device_ids), gallery, callback));
-  }
-
   // 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);
@@ -377,15 +357,15 @@ class ExtensionGalleriesHost
       if (!MediaStorageUtil::CanCreateFileSystem(device_id, path))
         continue;
 
-      std::string fs_name = MediaFileSystemBackend::ConstructMountName(
-          profile_path_, extension_id_, pref_id);
-      if (!file_system_context_->RegisterFileSystem(device_id, fs_name, path))
+      std::string fsid =
+          file_system_context_->RegisterFileSystem(device_id, path);
+      if (fsid.empty())
         continue;
 
       MediaFileSystemInfo new_entry(
           gallery_info.GetGalleryDisplayName(),
-          file_system_context_->GetRegisteredPath(fs_name),
-          fs_name,
+          path,
+          fsid,
           pref_id,
           GetTransientIdForRemovableDeviceId(device_id),
           StorageInfo::IsRemovableDevice(device_id),
@@ -403,46 +383,6 @@ class ExtensionGalleriesHost
     callback.Run(result);
   }
 
-  void RegisterAttachedMediaFileSystem(
-      const MediaStorageUtil::DeviceIdSet* attached_device,
-      const MediaGalleryPrefInfo& gallery,
-      const base::Callback<void(base::File::Error result)>& callback) {
-    base::File::Error result = base::File::FILE_ERROR_NOT_FOUND;
-
-    // If rph_refs is empty then we're actually in the middle of shutdown, and
-    // Filter...() lagging which can invoke this method interleaved in the
-    // destruction callback sequence and re-populate pref_id_map_.
-    if (!attached_device->empty() && !rph_refs_.empty()) {
-      std::string fs_name = MediaFileSystemBackend::ConstructMountName(
-          profile_path_, extension_id_, gallery.pref_id);
-      base::FilePath path = gallery.AbsolutePath();
-      const std::string& device_id = gallery.device_id;
-
-      if (ContainsKey(pref_id_map_, gallery.pref_id)) {
-        result = base::File::FILE_OK;
-      } else if (MediaStorageUtil::CanCreateFileSystem(device_id, path) &&
-                 file_system_context_->RegisterFileSystem(device_id, fs_name,
-                                                          path)) {
-        result = base::File::FILE_OK;
-        pref_id_map_[gallery.pref_id] = MediaFileSystemInfo(
-            gallery.GetGalleryDisplayName(),
-            file_system_context_->GetRegisteredPath(fs_name),
-            fs_name,
-            gallery.pref_id,
-            GetTransientIdForRemovableDeviceId(device_id),
-            StorageInfo::IsRemovableDevice(device_id),
-            StorageInfo::IsMediaDevice(device_id));
-      }
-    }
-
-    if (pref_id_map_.empty()) {
-      rph_refs_.Reset();
-      CleanUp();
-    }
-    BrowserThread::PostTask(BrowserThread::IO, FROM_HERE,
-                            base::Bind(callback, result));
-  }
-
   std::string GetTransientIdForRemovableDeviceId(const std::string& device_id) {
     if (!StorageInfo::IsRemovableDevice(device_id))
       return std::string();
@@ -466,12 +406,6 @@ class ExtensionGalleriesHost
   // safe to store a raw pointer.
   MediaFileSystemContext* file_system_context_;
 
-  // Path for the active profile.
-  const base::FilePath profile_path_;
-
-  // Id of the extension this host belongs to.
-  const std::string extension_id_;
-
   // A callback to call when the last RVH reference goes away.
   base::Closure no_references_callback_;
 
@@ -506,9 +440,22 @@ void MediaFileSystemRegistry::GetMediaFileSystemsForExtension(
     return;
   }
 
-  ExtensionGalleriesHost* extension_host =
-      GetExtensionGalleryHost(profile, preferences, extension->id());
+  ExtensionGalleriesHostMap::iterator extension_hosts =
+      extension_hosts_map_.find(profile);
+  if (extension_hosts->second.empty())
+    preferences->AddGalleryChangeObserver(this);
 
+  ExtensionGalleriesHost* extension_host =
+      extension_hosts->second[extension->id()].get();
+  if (!extension_host) {
+    extension_host = new ExtensionGalleriesHost(
+        file_system_context_.get(),
+        base::Bind(&MediaFileSystemRegistry::OnExtensionGalleriesHostEmpty,
+                   base::Unretained(this),
+                   profile,
+                   extension->id()));
+    extension_hosts_map_[profile][extension->id()] = extension_host;
+  }
   // This must come before the GetMediaFileSystems call to make sure the
   // RVH of the context is referenced before the filesystems are retrieved.
   extension_host->ReferenceFromRVH(rvh);
@@ -517,40 +464,6 @@ void MediaFileSystemRegistry::GetMediaFileSystemsForExtension(
                                       callback);
 }
 
-void MediaFileSystemRegistry::RegisterMediaFileSystemForExtension(
-    const content::RenderViewHost* rvh,
-    const extensions::Extension* extension,
-    MediaGalleryPrefId pref_id,
-    const base::Callback<void(base::File::Error result)>& callback) {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-  DCHECK_NE(kInvalidMediaGalleryPrefId, pref_id);
-
-  Profile* profile =
-      Profile::FromBrowserContext(rvh->GetProcess()->GetBrowserContext());
-  MediaGalleriesPreferences* preferences = GetPreferences(profile);
-  MediaGalleriesPrefInfoMap::const_iterator gallery =
-      preferences->known_galleries().find(pref_id);
-  MediaGalleryPrefIdSet permitted_galleries =
-      preferences->GalleriesForExtension(*extension);
-
-  if (gallery == preferences->known_galleries().end() ||
-      !ContainsKey(permitted_galleries, pref_id)) {
-    BrowserThread::PostTask(
-        BrowserThread::IO, FROM_HERE,
-        base::Bind(callback, base::File::FILE_ERROR_NOT_FOUND));
-    return;
-  }
-
-  ExtensionGalleriesHost* extension_host =
-      GetExtensionGalleryHost(profile, preferences, extension->id());
-
-  // This must come before the GetMediaFileSystems call to make sure the
-  // RVH of the context is referenced before the filesystems are retrieved.
-  extension_host->ReferenceFromRVH(rvh);
-
-  extension_host->RegisterMediaFileSystem(gallery->second, callback);
-}
-
 MediaGalleriesPreferences* MediaFileSystemRegistry::GetPreferences(
     Profile* profile) {
   // Create an empty ExtensionHostMap for this profile on first initialization.
@@ -625,49 +538,41 @@ void MediaFileSystemRegistry::OnRemovableStorageDetached(
 class MediaFileSystemRegistry::MediaFileSystemContextImpl
     : public MediaFileSystemContext {
  public:
-  MediaFileSystemContextImpl() {}
+  explicit MediaFileSystemContextImpl(MediaFileSystemRegistry* registry)
+      : registry_(registry) {
+    DCHECK(registry_);  // Suppresses unused warning on Android.
+  }
   virtual ~MediaFileSystemContextImpl() {}
 
-  virtual bool RegisterFileSystem(const std::string& device_id,
-                                  const std::string& fs_name,
-                                  const base::FilePath& path) OVERRIDE {
+  virtual std::string RegisterFileSystem(
+      const std::string& device_id, const base::FilePath& path) OVERRIDE {
     if (StorageInfo::IsMassStorageDevice(device_id)) {
-      return RegisterFileSystemForMassStorage(device_id, fs_name, path);
+      return RegisterFileSystemForMassStorage(device_id, path);
     } else {
-      return RegisterFileSystemForMTPDevice(device_id, fs_name, path);
+      return RegisterFileSystemForMTPDevice(device_id, path);
     }
   }
 
-  virtual void RevokeFileSystem(const std::string& fs_name) OVERRIDE {
+  virtual void RevokeFileSystem(const std::string& fsid) OVERRIDE {
     ImportedMediaGalleryRegistry* imported_registry =
         ImportedMediaGalleryRegistry::GetInstance();
-    if (imported_registry->RevokeImportedFilesystemOnUIThread(fs_name))
+    if (imported_registry->RevokeImportedFilesystemOnUIThread(fsid))
       return;
 
-    ExternalMountPoints::GetSystemInstance()->RevokeFileSystem(fs_name);
+    IsolatedContext::GetInstance()->RevokeFileSystem(fsid);
 
-    BrowserThread::PostTask(BrowserThread::IO, FROM_HERE, base::Bind(
-        &MTPDeviceMapService::RevokeMTPFileSystem,
-        base::Unretained(MTPDeviceMapService::GetInstance()),
-        fs_name));
-  }
-
-  virtual base::FilePath GetRegisteredPath(
-      const std::string& fs_name) const OVERRIDE {
-    base::FilePath result;
-    if (!ExternalMountPoints::GetSystemInstance()->GetRegisteredPath(fs_name,
-                                                                     &result)) {
-      return base::FilePath();
-    }
-    return result;
+    content::BrowserThread::PostTask(
+        content::BrowserThread::IO, FROM_HERE, base::Bind(
+            &MTPDeviceMapService::RevokeMTPFileSystem,
+            base::Unretained(MTPDeviceMapService::GetInstance()),
+            fsid));
   }
 
  private:
   // Registers and returns the file system id for the mass storage device
   // specified by |device_id| and |path|.
-  bool RegisterFileSystemForMassStorage(const std::string& device_id,
-                                        const std::string& fs_name,
-                                        const base::FilePath& path) {
+  std::string RegisterFileSystemForMassStorage(
+      const std::string& device_id, const base::FilePath& path) {
     DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
     DCHECK(StorageInfo::IsMassStorageDevice(device_id));
 
@@ -679,52 +584,57 @@ class MediaFileSystemRegistry::MediaFileSystemContextImpl
     // call tree, probably by having it figure out by device id what
     // registration is needed, or having per-device-type handlers at the
     // next higher level.
-    bool result = false;
+    std::string fsid;
     if (StorageInfo::IsITunesDevice(device_id)) {
-      ImportedMediaGalleryRegistry* registry =
+      ImportedMediaGalleryRegistry* imported_registry =
           ImportedMediaGalleryRegistry::GetInstance();
-      result = registry->RegisterITunesFilesystemOnUIThread(fs_name, path);
+      fsid = imported_registry->RegisterITunesFilesystemOnUIThread(path);
     } else if (StorageInfo::IsPicasaDevice(device_id)) {
-      ImportedMediaGalleryRegistry* registry =
+      ImportedMediaGalleryRegistry* imported_registry =
           ImportedMediaGalleryRegistry::GetInstance();
-      result = registry->RegisterPicasaFilesystemOnUIThread(fs_name, path);
+      fsid = imported_registry->RegisterPicasaFilesystemOnUIThread(
+          path);
     } else if (StorageInfo::IsIPhotoDevice(device_id)) {
-      ImportedMediaGalleryRegistry* registry =
+      ImportedMediaGalleryRegistry* imported_registry =
           ImportedMediaGalleryRegistry::GetInstance();
-      result = registry->RegisterIPhotoFilesystemOnUIThread(fs_name, path);
+      fsid = imported_registry->RegisterIPhotoFilesystemOnUIThread(
+          path);
     } else {
-      result = ExternalMountPoints::GetSystemInstance()->RegisterFileSystem(
-          fs_name, fileapi::kFileSystemTypeNativeMedia,
-          fileapi::FileSystemMountOption(), path);
+      std::string fs_name(extension_misc::kMediaFileSystemPathPart);
+      fsid = IsolatedContext::GetInstance()->RegisterFileSystemForPath(
+          fileapi::kFileSystemTypeNativeMedia, path, &fs_name);
     }
-    return result;
+    return fsid;
   }
 
-  bool RegisterFileSystemForMTPDevice(const std::string& device_id,
-                                      const std::string fs_name,
-                                      const base::FilePath& path) {
+  std::string RegisterFileSystemForMTPDevice(
+      const std::string& device_id, const base::FilePath& path) {
     DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
     DCHECK(!StorageInfo::IsMassStorageDevice(device_id));
 
     // Sanity checks for |path|.
     CHECK(MediaStorageUtil::CanCreateFileSystem(device_id, path));
-    bool result = ExternalMountPoints::GetSystemInstance()->RegisterFileSystem(
-        fs_name, fileapi::kFileSystemTypeDeviceMedia,
-        fileapi::FileSystemMountOption(), path);
-    CHECK(result);
-    BrowserThread::PostTask(BrowserThread::IO, FROM_HERE, base::Bind(
-        &MTPDeviceMapService::RegisterMTPFileSystem,
-        base::Unretained(MTPDeviceMapService::GetInstance()),
-        path.value(), fs_name));
-    return result;
+    std::string fs_name(extension_misc::kMediaFileSystemPathPart);
+    const std::string fsid =
+        IsolatedContext::GetInstance()->RegisterFileSystemForPath(
+            fileapi::kFileSystemTypeDeviceMedia, path, &fs_name);
+    CHECK(!fsid.empty());
+    content::BrowserThread::PostTask(
+        content::BrowserThread::IO, FROM_HERE, base::Bind(
+            &MTPDeviceMapService::RegisterMTPFileSystem,
+            base::Unretained(MTPDeviceMapService::GetInstance()),
+            path.value(), fsid));
+    return fsid;
   }
 
+  MediaFileSystemRegistry* registry_;
+
   DISALLOW_COPY_AND_ASSIGN(MediaFileSystemContextImpl);
 };
 
 // Constructor in 'private' section because depends on private class definition.
 MediaFileSystemRegistry::MediaFileSystemRegistry()
-    : file_system_context_(new MediaFileSystemContextImpl) {
+    : file_system_context_(new MediaFileSystemContextImpl(this)) {
   StorageMonitor::GetInstance()->AddObserver(this);
 }
 
@@ -788,33 +698,6 @@ void MediaFileSystemRegistry::OnGalleryRemoved(
   }
 }
 
-ExtensionGalleriesHost* MediaFileSystemRegistry::GetExtensionGalleryHost(
-    Profile* profile,
-    MediaGalleriesPreferences* preferences,
-    const std::string& extension_id) {
-  ExtensionGalleriesHostMap::iterator extension_hosts =
-      extension_hosts_map_.find(profile);
-  // GetPreferences(), which had to be called because preferences is an
-  // argument, ensures that profile is in the map.
-  DCHECK(extension_hosts != extension_hosts_map_.end());
-  if (extension_hosts->second.empty())
-    preferences->AddGalleryChangeObserver(this);
-
-  ExtensionGalleriesHost* result = extension_hosts->second[extension_id].get();
-  if (!result) {
-    result = new ExtensionGalleriesHost(
-        file_system_context_.get(),
-        profile->GetPath(),
-        extension_id,
-        base::Bind(&MediaFileSystemRegistry::OnExtensionGalleriesHostEmpty,
-                   base::Unretained(this),
-                   profile,
-                   extension_id));
-    extension_hosts_map_[profile][extension_id] = result;
-  }
-  return result;
-}
-
 void MediaFileSystemRegistry::OnExtensionGalleriesHostEmpty(
     Profile* profile, const std::string& extension_id) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
diff --git a/chrome/browser/media_galleries/media_file_system_registry.h b/chrome/browser/media_galleries/media_file_system_registry.h
index 9344698..04065ff 100644
--- a/chrome/browser/media_galleries/media_file_system_registry.h
+++ b/chrome/browser/media_galleries/media_file_system_registry.h
@@ -14,7 +14,6 @@
 #include <vector>
 
 #include "base/basictypes.h"
-#include "base/files/file.h"
 #include "base/files/file_path.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
@@ -81,14 +80,6 @@ class MediaFileSystemRegistry
       const extensions::Extension* extension,
       const MediaFileSystemsCallback& callback);
 
-  // Attempt to register the file system for |pref_id|. If |extension| does not
-  // have permission to |pref_id|, sends |callback| FILE_ERROR_NOT_FOUND.
-  void RegisterMediaFileSystemForExtension(
-      const content::RenderViewHost* rvh,
-      const extensions::Extension* extension,
-      MediaGalleryPrefId pref_id,
-      const base::Callback<void(base::File::Error result)>& callback);
-
   // Returns the media galleries preferences for the specified |profile|.
   // Caller is responsible for ensuring that the preferences are initialized
   // before use.
@@ -119,12 +110,6 @@ class MediaFileSystemRegistry
   virtual void OnGalleryRemoved(MediaGalleriesPreferences* pref,
                                 MediaGalleryPrefId pref_id) OVERRIDE;
 
-  // Look up or create the extension gallery host.
-  ExtensionGalleriesHost* GetExtensionGalleryHost(
-      Profile* profile,
-      MediaGalleriesPreferences* preferences,
-      const std::string& extension_id);
-
   void OnExtensionGalleriesHostEmpty(Profile* profile,
                                      const std::string& extension_id);
 
diff --git a/chrome/browser/media_galleries/media_file_system_registry_unittest.cc b/chrome/browser/media_galleries/media_file_system_registry_unittest.cc
index 0bc622a..f771d6a 100644
--- a/chrome/browser/media_galleries/media_file_system_registry_unittest.cc
+++ b/chrome/browser/media_galleries/media_file_system_registry_unittest.cc
@@ -65,47 +65,47 @@ class TestMediaFileSystemContext : public MediaFileSystemContext {
   struct FSInfo {
     FSInfo() {}
     FSInfo(const std::string& device_id, const base::FilePath& path,
-           const std::string& fs_name);
+           const std::string& fsid);
 
     bool operator<(const FSInfo& other) const;
 
     std::string device_id;
     base::FilePath path;
-    std::string fs_name;
+    std::string fsid;
   };
 
   explicit TestMediaFileSystemContext(MediaFileSystemRegistry* registry);
   virtual ~TestMediaFileSystemContext() {}
 
   // MediaFileSystemContext implementation.
-  virtual bool RegisterFileSystem(const std::string& device_id,
-                                  const std::string& fs_name,
-                                  const base::FilePath& path) OVERRIDE;
+  virtual std::string RegisterFileSystem(
+      const std::string& device_id, const base::FilePath& path) OVERRIDE;
 
-  virtual void RevokeFileSystem(const std::string& fs_name) OVERRIDE;
+  virtual void RevokeFileSystem(const std::string& fsid) OVERRIDE;
 
-  virtual base::FilePath GetRegisteredPath(
-      const std::string& fs_name) const OVERRIDE;
+  base::FilePath GetPathForId(const std::string& fsid) const;
 
   MediaFileSystemRegistry* registry() { return registry_; }
 
  private:
-  void AddFSEntry(const std::string& device_id,
-                  const base::FilePath& path,
-                  const std::string& fs_name);
+  std::string AddFSEntry(const std::string& device_id,
+                         const base::FilePath& path);
 
   MediaFileSystemRegistry* registry_;
 
+  // A counter used to construct mock FSIDs.
+  int fsid_;
+
   // The currently allocated mock file systems.
-  std::map<std::string /*fs_name*/, FSInfo> file_systems_by_name_;
+  std::map<std::string /*fsid*/, FSInfo> file_systems_by_id_;
 };
 
 TestMediaFileSystemContext::FSInfo::FSInfo(const std::string& device_id,
                                            const base::FilePath& path,
-                                           const std::string& fs_name)
+                                           const std::string& fsid)
     : device_id(device_id),
       path(path),
-      fs_name(fs_name) {
+      fsid(fsid) {
 }
 
 bool TestMediaFileSystemContext::FSInfo::operator<(const FSInfo& other) const {
@@ -113,47 +113,47 @@ bool TestMediaFileSystemContext::FSInfo::operator<(const FSInfo& other) const {
     return device_id < other.device_id;
   if (path.value() != other.path.value())
     return path.value() < other.path.value();
-  return fs_name < other.fs_name;
+  return fsid < other.fsid;
 }
 
 TestMediaFileSystemContext::TestMediaFileSystemContext(
     MediaFileSystemRegistry* registry)
-    : registry_(registry) {
+    : registry_(registry),
+      fsid_(0) {
   registry_->file_system_context_.reset(this);
 }
 
-bool TestMediaFileSystemContext::RegisterFileSystem(
-    const std::string& device_id,
-    const std::string& fs_name,
-    const base::FilePath& path) {
-  AddFSEntry(device_id, path, fs_name);
-  return true;
+std::string TestMediaFileSystemContext::RegisterFileSystem(
+    const std::string& device_id, const base::FilePath& path) {
+  std::string fsid = AddFSEntry(device_id, path);
+  return fsid;
 }
 
-void TestMediaFileSystemContext::RevokeFileSystem(const std::string& fs_name) {
-  if (!ContainsKey(file_systems_by_name_, fs_name))
+void TestMediaFileSystemContext::RevokeFileSystem(const std::string& fsid) {
+  if (!ContainsKey(file_systems_by_id_, fsid))
     return;
-  EXPECT_EQ(1U, file_systems_by_name_.erase(fs_name));
+  EXPECT_EQ(1U, file_systems_by_id_.erase(fsid));
 }
 
-base::FilePath TestMediaFileSystemContext::GetRegisteredPath(
-    const std::string& fs_name) const {
-  std::map<std::string /*fs_name*/, FSInfo>::const_iterator it =
-      file_systems_by_name_.find(fs_name);
-  if (it == file_systems_by_name_.end())
+base::FilePath TestMediaFileSystemContext::GetPathForId(
+    const std::string& fsid) const {
+  std::map<std::string /*fsid*/, FSInfo>::const_iterator it =
+      file_systems_by_id_.find(fsid);
+  if (it == file_systems_by_id_.end())
     return base::FilePath();
   return it->second.path;
 }
 
-void TestMediaFileSystemContext::AddFSEntry(const std::string& device_id,
-                                            const base::FilePath& path,
-                                            const std::string& fs_name) {
+std::string TestMediaFileSystemContext::AddFSEntry(const std::string& device_id,
+                                                   const base::FilePath& path) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
   DCHECK(path.IsAbsolute());
   DCHECK(!path.ReferencesParent());
 
-  FSInfo info(device_id, path, fs_name);
-  file_systems_by_name_[fs_name] = info;
+  std::string fsid = base::StringPrintf("FSID:%d", ++fsid_);
+  FSInfo info(device_id, path, fsid);
+  file_systems_by_id_[fsid] = info;
+  return fsid;
 }
 
 namespace {
@@ -184,7 +184,7 @@ void CheckGalleryInfo(const MediaFileSystemInfo& info,
   else
     EXPECT_EQ(0UL, info.transient_device_id.size());
 
-  base::FilePath fsid_path = fs_context->GetRegisteredPath(info.fsid);
+  base::FilePath fsid_path = fs_context->GetPathForId(info.fsid);
   EXPECT_EQ(path, fsid_path);
 }
 
@@ -1067,7 +1067,7 @@ TEST_F(MediaFileSystemRegistryTest, PreferenceListener) {
   FSInfoMap fs_info = profile_state->GetGalleriesInfo(
       profile_state->regular_permission_extension());
   ASSERT_EQ(1U, fs_info.size());
-  EXPECT_FALSE(test_file_system_context()->GetRegisteredPath(
+  EXPECT_FALSE(test_file_system_context()->GetPathForId(
       fs_info.begin()->second.fsid).empty());
 
   // Revoke permission and ensure that the file system is revoked.
@@ -1075,6 +1075,6 @@ TEST_F(MediaFileSystemRegistryTest, PreferenceListener) {
                        profile_state->regular_permission_extension(),
                        device_id,
                        false /*has access*/);
-  EXPECT_TRUE(test_file_system_context()->GetRegisteredPath(
+  EXPECT_TRUE(test_file_system_context()->GetPathForId(
       fs_info.begin()->second.fsid).empty());
 }
diff --git a/chrome/browser/media_galleries/media_galleries_preferences.cc b/chrome/browser/media_galleries/media_galleries_preferences.cc
index 9ab57f4..e5b05ae 100644
--- a/chrome/browser/media_galleries/media_galleries_preferences.cc
+++ b/chrome/browser/media_galleries/media_galleries_preferences.cc
@@ -20,7 +20,6 @@
 #include "chrome/browser/extensions/extension_service.h"
 #include "chrome/browser/media_galleries/fileapi/iapps_finder.h"
 #include "chrome/browser/media_galleries/fileapi/picasa_finder.h"
-#include "chrome/browser/media_galleries/imported_media_gallery_registry.h"
 #include "chrome/browser/media_galleries/media_file_system_registry.h"
 #include "chrome/browser/media_galleries/media_galleries_histograms.h"
 #include "chrome/browser/profiles/profile.h"
@@ -307,11 +306,6 @@ base::string16 GetDisplayNameForSubFolder(const base::string16& device_name,
           device_name);
 }
 
-void InitializeImportedMediaGalleryRegistryOnFileThread() {
-  DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::FILE));
-  ImportedMediaGalleryRegistry::GetInstance()->Initialize();
-}
-
 }  // namespace
 
 MediaGalleryPrefInfo::MediaGalleryPrefInfo()
@@ -581,7 +575,7 @@ void MediaGalleriesPreferences::OnStorageMonitorInit(
 }
 
 void MediaGalleriesPreferences::OnFinderDeviceID(const std::string& device_id) {
-  if (!device_id.empty()) {
+  if (!device_id.empty() && !UpdateDeviceIDForSingletonType(device_id)) {
     std::string gallery_name;
     if (StorageInfo::IsIPhotoDevice(device_id))
       gallery_name = kIPhotoGalleryName;
@@ -589,25 +583,13 @@ void MediaGalleriesPreferences::OnFinderDeviceID(const std::string& device_id) {
       gallery_name = kITunesGalleryName;
     else if (StorageInfo::IsPicasaDevice(device_id))
       gallery_name = kPicasaGalleryName;
+    else
+      NOTREACHED();
 
-    if (!gallery_name.empty()) {
-      pre_initialization_callbacks_waiting_++;
-      content::BrowserThread::PostTaskAndReply(
-          content::BrowserThread::FILE,
-          FROM_HERE,
-          base::Bind(&InitializeImportedMediaGalleryRegistryOnFileThread),
-          base::Bind(
-              &MediaGalleriesPreferences::OnInitializationCallbackReturned,
-              weak_factory_.GetWeakPtr()));
-    }
-
-    if (!UpdateDeviceIDForSingletonType(device_id)) {
-      DCHECK(!gallery_name.empty());
-      AddGalleryInternal(device_id, base::ASCIIToUTF16(gallery_name),
-                         base::FilePath(), MediaGalleryPrefInfo::kAutoDetected,
-                         base::string16(), base::string16(), base::string16(),
-                         0, base::Time(), false, 0, 0, 0, kCurrentPrefsVersion);
-    }
+    AddGalleryInternal(device_id, base::ASCIIToUTF16(gallery_name),
+                       base::FilePath(), MediaGalleryPrefInfo::kAutoDetected,
+                       base::string16(), base::string16(), base::string16(), 0,
+                       base::Time(), false, 0, 0, 0, kCurrentPrefsVersion);
   }
 
   OnInitializationCallbackReturned();
diff --git a/chrome/renderer/extensions/media_galleries_custom_bindings.cc b/chrome/renderer/extensions/media_galleries_custom_bindings.cc
index 78a4e27..1b4a0e1 100644
--- a/chrome/renderer/extensions/media_galleries_custom_bindings.cc
+++ b/chrome/renderer/extensions/media_galleries_custom_bindings.cc
@@ -23,22 +23,21 @@ void GetMediaFileSystemObject(const v8::FunctionCallbackInfo<v8::Value>& args) {
   CHECK_EQ(1, args.Length());
   CHECK(args[0]->IsString());
 
-  std::string fs_mount(*v8::String::Utf8Value(args[0]));
-  CHECK(!fs_mount.empty());
+  std::string fsid(*v8::String::Utf8Value(args[0]));
+  CHECK(!fsid.empty());
 
   blink::WebFrame* webframe = blink::WebFrame::frameForCurrentContext();
   const GURL origin = GURL(webframe->document().securityOrigin().toString());
-  std::string fs_name =
-      fileapi::GetFileSystemName(origin, fileapi::kFileSystemTypeExternal);
-  fs_name.append("_");
-  fs_name.append(fs_mount);
+  const std::string fs_name = fileapi::GetIsolatedFileSystemName(origin, fsid);
   const GURL root_url(
-      fileapi::GetExternalFileSystemRootURIString(origin, fs_mount));
+      fileapi::GetIsolatedFileSystemRootURIString(
+          origin, fsid, extension_misc::kMediaFileSystemPathPart));
   args.GetReturnValue().Set(
-      blink::WebDOMFileSystem::create(webframe,
-                                      blink::WebFileSystemTypeExternal,
-                                      blink::WebString::fromUTF8(fs_name),
-                                      root_url).toV8Value());
+      blink::WebDOMFileSystem::create(
+          webframe,
+          blink::WebFileSystemTypeIsolated,
+          blink::WebString::fromUTF8(fs_name),
+          root_url).toV8Value());
 }
 
 }  // namespace
diff --git a/chrome/test/data/extensions/api_test/media_galleries/tourl/manifest.json b/chrome/test/data/extensions/api_test/media_galleries/tourl/manifest.json
deleted file mode 100644
index ee63b20..0000000
--- a/chrome/test/data/extensions/api_test/media_galleries/tourl/manifest.json
+++ /dev/null
@@ -1,11 +0,0 @@
-{
-  "name": "chrome.mediaGalleries.tourl",
-  "version": "0.1",
-  "description": "test url access for chrome.mediaGalleries",
-  "app": {
-    "background": {
-      "scripts": ["common_injected.js", "test.js"]
-    }
-  },
-  "permissions": [{"mediaGalleries": ["read", "allAutoDetected"]}]
-}
diff --git a/chrome/test/data/extensions/api_test/media_galleries/tourl/test.js b/chrome/test/data/extensions/api_test/media_galleries/tourl/test.js
deleted file mode 100644
index 43baf0f..0000000
--- a/chrome/test/data/extensions/api_test/media_galleries/tourl/test.js
+++ /dev/null
@@ -1,51 +0,0 @@
-// Copyright 2014 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.
-
-function check_result_factory(expected) {
-  return function() {
-    if (expected) {
-      chrome.test.succeed();
-    } else {
-      chrome.test.fail();
-    }
-  };
-}
-
-function TestImageLoadFactory(url, should_load) {
-  return function() {
-    test_image = document.createElement('img');
-    document.body.appendChild(test_image);
-    test_image.addEventListener('load', check_result_factory(should_load));
-    test_image.addEventListener('error', check_result_factory(!should_load));
-
-    test_image.src = url;
-  };
-}
-
-CreateDummyWindowToPreventSleep();
-
-chrome.test.getConfig(function(config) {
-  var customArg = JSON.parse(config.customArg);
-  var gallery_id = customArg[0];
-  var profile_path = customArg[1];
-  var extension_url = chrome.runtime.getURL('/');
-  var extension_id = extension_url.split('/')[2];
-
-  var bad_mount_point = 'filesystem:' + extension_url +
-    'external/invalid-' + profile_path + '-' + extension_id + '-' + gallery_id +
-    '/test.jpg';
-
-  var bad_mount_name = 'filesystem:' + extension_url +
-    'external/media_galleries-' + profile_path + '-' + gallery_id + '/test.jpg';
-
-  var good_url = 'filesystem:' + extension_url +
-    'external/media_galleries-' + profile_path + '-' + extension_id + '-' +
-    gallery_id + '/test.jpg';
-
-  chrome.test.runTests([
-    TestImageLoadFactory(bad_mount_point, false),
-    TestImageLoadFactory(bad_mount_name, false),
-    TestImageLoadFactory(good_url, true),
-  ]);
-})
diff --git a/components/storage_monitor/media_storage_util.cc b/components/storage_monitor/media_storage_util.cc
index c95f534..20190d4 100644
--- a/components/storage_monitor/media_storage_util.cc
+++ b/components/storage_monitor/media_storage_util.cc
@@ -116,7 +116,7 @@ bool MediaStorageUtil::CanCreateFileSystem(const std::string& device_id,
   if (type == StorageInfo::MAC_IMAGE_CAPTURE)
     return true;
 
-  return !path.empty() && path.IsAbsolute() && !path.ReferencesParent();
+  return path.IsAbsolute() && !path.ReferencesParent();
 }
 
 // static
diff --git a/components/storage_monitor/media_storage_util_unittest.cc b/components/storage_monitor/media_storage_util_unittest.cc
index d16cd07..aa0f37c 100644
--- a/components/storage_monitor/media_storage_util_unittest.cc
+++ b/components/storage_monitor/media_storage_util_unittest.cc
@@ -119,8 +119,6 @@ TEST_F(MediaStorageUtilTest, CanCreateFileSystemForImageCapture) {
   EXPECT_TRUE(MediaStorageUtil::CanCreateFileSystem(kImageCaptureDeviceId,
                                                     base::FilePath()));
   EXPECT_FALSE(MediaStorageUtil::CanCreateFileSystem(
-      "dcim:xyz", base::FilePath()));
-  EXPECT_FALSE(MediaStorageUtil::CanCreateFileSystem(
       "dcim:xyz", base::FilePath(FILE_PATH_LITERAL("relative"))));
   EXPECT_FALSE(MediaStorageUtil::CanCreateFileSystem(
       "dcim:xyz", base::FilePath(FILE_PATH_LITERAL("../refparent"))));
diff --git a/content/browser/child_process_security_policy_impl.cc b/content/browser/child_process_security_policy_impl.cc
index cadd31c..c6200dd 100644
--- a/content/browser/child_process_security_policy_impl.cc
+++ b/content/browser/child_process_security_policy_impl.cc
@@ -461,16 +461,6 @@ void ChildProcessSecurityPolicyImpl::GrantCreateReadWriteFile(
   GrantPermissionsForFile(child_id, file, CREATE_READ_WRITE_FILE_GRANT);
 }
 
-void ChildProcessSecurityPolicyImpl::GrantCopyInto(int child_id,
-                                                   const base::FilePath& dir) {
-  GrantPermissionsForFile(child_id, dir, COPY_INTO_FILE_GRANT);
-}
-
-void ChildProcessSecurityPolicyImpl::GrantDeleteFrom(
-    int child_id, const base::FilePath& dir) {
-  GrantPermissionsForFile(child_id, dir, DELETE_FILE_GRANT);
-}
-
 void ChildProcessSecurityPolicyImpl::GrantPermissionsForFile(
     int child_id, const base::FilePath& file, int permissions) {
   base::AutoLock lock(lock_);
diff --git a/content/browser/child_process_security_policy_impl.h b/content/browser/child_process_security_policy_impl.h
index 005292c..db640d8 100644
--- a/content/browser/child_process_security_policy_impl.h
+++ b/content/browser/child_process_security_policy_impl.h
@@ -45,9 +45,6 @@ class CONTENT_EXPORT ChildProcessSecurityPolicyImpl
   virtual void GrantReadFile(int child_id, const base::FilePath& file) OVERRIDE;
   virtual void GrantCreateReadWriteFile(int child_id,
                                         const base::FilePath& file) OVERRIDE;
-  virtual void GrantCopyInto(int child_id, const base::FilePath& dir) OVERRIDE;
-  virtual void GrantDeleteFrom(int child_id,
-                               const base::FilePath& dir) OVERRIDE;
   virtual void GrantReadFileSystem(
       int child_id,
       const std::string& filesystem_id) OVERRIDE;
diff --git a/content/public/browser/child_process_security_policy.h b/content/public/browser/child_process_security_policy.h
index 261bf58..2f462b2 100644
--- a/content/public/browser/child_process_security_policy.h
+++ b/content/public/browser/child_process_security_policy.h
@@ -51,12 +51,6 @@ class ChildProcessSecurityPolicy {
   virtual void GrantCreateReadWriteFile(int child_id,
                                         const base::FilePath& file) = 0;
 
-  // This permission grants copy-into permission for |dir|.
-  virtual void GrantCopyInto(int child_id, const base::FilePath& dir) = 0;
-
-  // This permission grants delete permission for |dir|.
-  virtual void GrantDeleteFrom(int child_id, const base::FilePath& dir) = 0;
-
   // These methods verify whether or not the child process has been granted
   // permissions perform these functions on |file|.
 
diff --git a/webkit/browser/fileapi/file_system_context.cc b/webkit/browser/fileapi/file_system_context.cc
index f6e7df3..3c75a8b 100644
--- a/webkit/browser/fileapi/file_system_context.cc
+++ b/webkit/browser/fileapi/file_system_context.cc
@@ -78,17 +78,15 @@ int FileSystemContext::GetPermissionPolicy(FileSystemType type) {
       return FILE_PERMISSION_READ_ONLY |
              FILE_PERMISSION_USE_FILE_PERMISSION;
 
+    // Following types are only accessed via IsolatedFileSystem, and
+    // don't have their own permission policies.
     case kFileSystemTypeDeviceMedia:
+    case kFileSystemTypeDragged:
+    case kFileSystemTypeForTransientFile:
     case kFileSystemTypeIphoto:
     case kFileSystemTypeItunes:
     case kFileSystemTypeNativeMedia:
     case kFileSystemTypePicasa:
-      return FILE_PERMISSION_USE_FILE_PERMISSION;
-
-    // Following types are only accessed via IsolatedFileSystem, and
-    // don't have their own permission policies.
-    case kFileSystemTypeDragged:
-    case kFileSystemTypeForTransientFile:
     case kFileSystemTypePluginPrivate:
       return FILE_PERMISSION_ALWAYS_DENY;