diff -r 000000000000 -r 6474c204b198 dom/filesystem/FileSystemUtils.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dom/filesystem/FileSystemUtils.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,76 @@
+/* -*- Mode: c++; c-basic-offset: 2; indent-tabs-mode: nil; tab-width: 40 -*- */
+/* vim: set ts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/dom/FileSystemUtils.h"
+
+#include "nsXULAppAPI.h"
+
+namespace mozilla {
+namespace dom {
+
+// static
+void
+FileSystemUtils::LocalPathToNormalizedPath(const nsAString& aLocal,
+                                           nsAString& aNorm)
+{
+  nsString result;
+  result = aLocal;
+#if defined(XP_WIN)
+  char16_t* cur = result.BeginWriting();
+  char16_t* end = result.EndWriting();
+  for (; cur < end; ++cur) {
+    if (char16_t('\\') == *cur)
+      *cur = char16_t('/');
+  }
+#endif
+  aNorm = result;
+}
+
+// static
+void
+FileSystemUtils::NormalizedPathToLocalPath(const nsAString& aNorm,
+                                           nsAString& aLocal)
+{
+  nsString result;
+  result = aNorm;
+#if defined(XP_WIN)
+  char16_t* cur = result.BeginWriting();
+  char16_t* end = result.EndWriting();
+  for (; cur < end; ++cur) {
+    if (char16_t('/') == *cur)
+      *cur = char16_t('\\');
+  }
+#endif
+  aLocal = result;
+}
+
+// static
+bool
+FileSystemUtils::IsDescendantPath(const nsAString& aPath,
+                                  const nsAString& aDescendantPath)
+{
+  // The descendant path should begin with its ancestor path.
+  nsAutoString prefix;
+  prefix = aPath + NS_LITERAL_STRING(FILESYSTEM_DOM_PATH_SEPARATOR);
+
+  // Check the sub-directory path to see if it has the parent path as prefix.
+  if (aDescendantPath.Length() < prefix.Length() ||
+      !StringBeginsWith(aDescendantPath, prefix)) {
+    return false;
+  }
+
+  return true;
+}
+
+// static
+bool
+FileSystemUtils::IsParentProcess()
+{
+  return XRE_GetProcessType() == GeckoProcessType_Default;
+}
+
+} // namespace dom
+} // namespace mozilla