arc: Add URL converter functions

chrome/browser/chromeos/arc/fileapi/arc_content_file_system_url_util.cc

+// Copyright 2016 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/chromeos/arc/fileapi/arc_content_file_system_url_util.h"
+
+#include "base/files/file_path.h"
+#include "chrome/browser/chromeos/fileapi/external_file_url_util.h"
+#include "net/base/escape.h"
+
+namespace arc {
+
+const char kMountPointName[] = "arc-content";

[mtomasz, 2016/10/20 08:55:05]

nit: Can this be constexpr and/or anonymous namespace?

[hashimoto, 2016/10/20 09:26:45]

Later this will be used to add a mount to chromeos::FileSystemBackend, though
ATM it's only used in this file.
Put it into an anonymous namespace

+
+GURL ArcUrlToExternalFileUrl(const GURL& arc_url) {
+  // Return "externalfile:arc-content/<|arc_url| escaped>".
+  base::FilePath virtual_path =
+      base::FilePath::FromUTF8Unsafe(kMountPointName)
+          .Append(base::FilePath::FromUTF8Unsafe(
+              net::EscapeQueryParamValue(arc_url.spec(), false)));
+  return chromeos::VirtualPathToExternalFileURL(virtual_path);
+}
+
+GURL ExternalFileUrlToArcUrl(const GURL& external_file_url) {
+  base::FilePath virtual_path =
+      chromeos::ExternalFileURLToVirtualPath(external_file_url);
+  base::FilePath path_after_root;
+  if (!base::FilePath::FromUTF8Unsafe(kMountPointName)
+           .AppendRelativePath(virtual_path, &path_after_root)) {
+    return GURL();
+  }
+  return GURL(net::UnescapeURLComponent(
+      path_after_root.AsUTF8Unsafe(),
+      net::UnescapeRule::SPACES | net::UnescapeRule::PATH_SEPARATORS |
+          net::UnescapeRule::URL_SPECIAL_CHARS_EXCEPT_PATH_SEPARATORS));
+}
+
+}  // namespace arc