This is UI side unreadable device support.

chrome/browser/extensions/extension_file_browser_private_api.cc

 // Copyright (c) 2011 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.
 
 #include "chrome/browser/extensions/extension_file_browser_private_api.h"
 
 #include "base/base64.h"
 #include "base/command_line.h"
 #include "base/json/json_writer.h"
 #include "base/logging.h"
@@ skipping 250 matching lines @@
 
     FilePath relative_mount_path;
     // Convert mount point path to relative path with the external file system
     // exposed within File API.
     if (FileManagerUtil::ConvertFileToRelativeFileSystemPath(profile,
             FilePath(mount_point_info.mount_path),
             &relative_mount_path)) {
       mount_info->SetString("mountPath", relative_mount_path.value());
     }
 
+    mount_info->SetString("mountCondition",
+        chromeos::MountLibrary::MountConditionToString(
+        mount_point_info.mount_condition));
+
     return mount_info;
 }
 #endif
 
 
 class LocalFileSystemCallbackDispatcher
     : public fileapi::FileSystemCallbackDispatcher {
  public:
   explicit LocalFileSystemCallbackDispatcher(
       RequestLocalFileSystemFunction* function,
@@ skipping 1058 matching lines @@
   chromeos::MountLibrary* mount_lib =
       chromeos::CrosLibrary::Get()->GetMountLibrary();
   chromeos::MountLibrary::DiskMap::const_iterator volume_it =
       mount_lib->disks().find(volume_device_path);
 
   if (volume_it != mount_lib->disks().end()) {
     chromeos::MountLibrary::Disk* volume = volume_it->second;
     DictionaryValue* volume_info = new DictionaryValue();
     result_.reset(volume_info);
     // Localising mount path.
-    FilePath relative_mount_path;
-    FileManagerUtil::ConvertFileToRelativeFileSystemPath(profile_,
-        FilePath(volume->mount_path()), &relative_mount_path);
-
+    std::string mount_path;
+    if (!volume->mount_path().empty()) {
+      FilePath relative_mount_path;
+      FileManagerUtil::ConvertFileToRelativeFileSystemPath(profile_,
+          FilePath(volume->mount_path()), &relative_mount_path);
+      mount_path = relative_mount_path.value();
+    }
     volume_info->SetString("devicePath", volume->device_path());
-    volume_info->SetString("mountPath", relative_mount_path.value());
+    volume_info->SetString("mountPath", mount_path);
     volume_info->SetString("systemPath", volume->system_path());
     volume_info->SetString("filePath", volume->file_path());
     volume_info->SetString("deviceLabel", volume->device_label());
     volume_info->SetString("driveLabel", volume->drive_label());
     volume_info->SetString("deviceType",
         DeviceTypeToString(volume->device_type()));
     volume_info->SetInteger("totalSize", volume->total_size());
     volume_info->SetBoolean("isParent", volume->is_parent());
     volume_info->SetBoolean("isReadOnly", volume->is_read_only());
     volume_info->SetBoolean("hasMedia", volume->has_media());
@@ skipping 105 matching lines @@
   SET_STRING(IDS_FILE_BROWSER, OPEN_LABEL);
   SET_STRING(IDS_FILE_BROWSER, SAVE_LABEL);
   SET_STRING(IDS_FILE_BROWSER, OK_LABEL);
 
   SET_STRING(IDS_FILE_BROWSER, DEFAULT_NEW_FOLDER_NAME);
   SET_STRING(IDS_FILE_BROWSER, MORE_FILES);
 
   SET_STRING(IDS_FILE_BROWSER, CONFIRM_DELETE_ONE);
   SET_STRING(IDS_FILE_BROWSER, CONFIRM_DELETE_SOME);
 
+  SET_STRING(IDS_FILE_BROWSER, UNKNOWN_FILESYSTEM_WARNING);
+  SET_STRING(IDS_FILE_BROWSER, UNSUPPORTED_FILESYSTEM_WARNING);
   SET_STRING(IDS_FILE_BROWSER, FORMATTING_WARNING);
 
   SET_STRING(IDS_FILE_BROWSER, SELECT_FOLDER_TITLE);
   SET_STRING(IDS_FILE_BROWSER, SELECT_OPEN_FILE_TITLE);
   SET_STRING(IDS_FILE_BROWSER, SELECT_OPEN_MULTI_FILE_TITLE);
   SET_STRING(IDS_FILE_BROWSER, SELECT_SAVEAS_FILE_TITLE);
 
   SET_STRING(IDS_FILE_BROWSER, COMPUTING_SELECTION);
   SET_STRING(IDS_FILE_BROWSER, NOTHING_SELECTED);
   SET_STRING(IDS_FILE_BROWSER, ONE_FILE_SELECTED);
@@ skipping 35 matching lines @@
   // TODO(serya): Create a new string in .grd file for this one in M13.
   dict->SetString("PREVIEW_IMAGE",
       l10n_util::GetStringUTF16(IDS_CERT_MANAGER_VIEW_CERT_BUTTON));
   dict->SetString("PLAY_MEDIA",
       l10n_util::GetStringUTF16(IDS_CONTENT_CONTEXT_PLAY));
   if (CommandLine::ForCurrentProcess()->HasSwitch(switches::kEnableArchives))
     dict->SetString("ENABLE_ARCHIVES", "true");
 
   return true;
 }