arc: Add URL converter functions

chrome/browser/chromeos/fileapi/external_file_url_util.h

Index: chrome/browser/chromeos/fileapi/external_file_url_util.h
diff --git a/chrome/browser/chromeos/fileapi/external_file_url_util.h b/chrome/browser/chromeos/fileapi/external_file_url_util.h
index afcf8ca858c6a8e61b2ea37b857748055e537aaf..3d01da511e18e17c241e752692004e52e157068d 100644
--- a/chrome/browser/chromeos/fileapi/external_file_url_util.h
+++ b/chrome/browser/chromeos/fileapi/external_file_url_util.h
@@ -32,6 +32,9 @@ GURL FileSystemURLToExternalFileURL(
 // Converts a externalfile: URL back to a virtual path of FileSystemURL.
 base::FilePath ExternalFileURLToVirtualPath(const GURL& url);
 
+// Converts a virtual path of FileSystemURL to an externalfile: URL.
+GURL VirtualPathToExternalFileURL(const base::FilePath& virtual_path);
+
 // Obtains external file URL (e.g. external:drive/root/sample.txt) from file
 // path (e.g. /special/drive-xxx/root/sample.txt), if the |path| points an
 // external location (drive, MTP, or FSP). Otherwise, it returns empty URL.