This is UI side unreadable device support.

chrome/browser/extensions/extension_file_browser_private_api.cc

Index: chrome/browser/extensions/extension_file_browser_private_api.cc
diff --git a/chrome/browser/extensions/extension_file_browser_private_api.cc b/chrome/browser/extensions/extension_file_browser_private_api.cc
index f64321e82460d500ddccce9d7a640f95c8acec7c..7ba8d635d81aa923af473a6d72225dfd53d923ac 100644
--- a/chrome/browser/extensions/extension_file_browser_private_api.cc
+++ b/chrome/browser/extensions/extension_file_browser_private_api.cc
@@ -268,6 +268,8 @@ base::DictionaryValue* MountPointToValue(Profile* profile,
       mount_info->SetString("mountPath", relative_mount_path.value());
     }
 
+    mount_info->SetString("specialData",  mount_point_info.special_data);
+
     return mount_info;
 }
 #endif
@@ -1318,6 +1320,32 @@ void FormatDeviceFunction::GetLocalPathsResponseOnUIThread(
   SendResponse(true);
 }
 
+FormatUnmountedDeviceFunction::FormatUnmountedDeviceFunction() {
+}
+
+FormatUnmountedDeviceFunction::~FormatUnmountedDeviceFunction() {
+}
+
+bool FormatUnmountedDeviceFunction::RunImpl() {
+  if (args_->GetSize() != 1) {
+    return false;
+  }
+
+  std::string volume_file;
+  if (!args_->GetString(0, &volume_file)) {
+    NOTREACHED();
+    return false;
+  }
+
+#ifdef OS_CHROMEOS
+  chromeos::CrosLibrary::Get()->GetMountLibrary()->FormatUnmountedDevice(
+      volume_file.c_str());
+#endif
+
+  SendResponse(true);
+  return true;
+}
+
 GetVolumeMetadataFunction::GetVolumeMetadataFunction() {
 }
 
@@ -1346,12 +1374,17 @@ bool GetVolumeMetadataFunction::RunImpl() {
     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();
+    } else {
+      mount_path = "unmounted";
+    }
     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());
@@ -1477,6 +1510,8 @@ bool FileDialogStringsFunction::RunImpl() {
   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);