diff -r 000000000000 -r 6474c204b198 xpcom/base/nsSetDllDirectory.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/xpcom/base/nsSetDllDirectory.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,42 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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/. */
+
+#ifndef nsSetDllDirectory_h
+#define nsSetDllDirectory_h
+
+#ifndef XP_WIN
+#error This file only makes sense on Windows.
+#endif
+
+#include <windows.h>
+#include <nscore.h>
+#include <stdlib.h>
+
+namespace mozilla {
+
+static void SanitizeEnvironmentVariables()
+{
+  DWORD bufferSize = GetEnvironmentVariableW(L"PATH", nullptr, 0);
+  if (bufferSize) {
+    wchar_t* originalPath = new wchar_t[bufferSize];
+    if (bufferSize - 1 == GetEnvironmentVariableW(L"PATH", originalPath, bufferSize)) {
+      bufferSize = ExpandEnvironmentStringsW(originalPath, nullptr, 0);
+      if (bufferSize) {
+        wchar_t* newPath = new wchar_t[bufferSize];
+        if (ExpandEnvironmentStringsW(originalPath,
+                                      newPath,
+                                      bufferSize)) {
+          SetEnvironmentVariableW(L"PATH", newPath);
+        }
+        delete[] newPath;
+      }
+    }
+    delete[] originalPath;
+  }
+}
+
+}
+
+#endif