diff -r 000000000000 -r 6474c204b198 ipc/glue/ScopedXREEmbed.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/ipc/glue/ScopedXREEmbed.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,113 @@
+/* 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 "ScopedXREEmbed.h"
+
+#include "base/command_line.h"
+#include "base/string_util.h"
+
+#include "nsIFile.h"
+
+#include "nsCOMPtr.h"
+#include "nsServiceManagerUtils.h"
+#include "nsString.h"
+#include "nsXULAppAPI.h"
+
+using mozilla::ipc::ScopedXREEmbed;
+
+ScopedXREEmbed::ScopedXREEmbed()
+: mShouldKillEmbedding(false)
+{
+  NS_LogInit();
+}
+
+ScopedXREEmbed::~ScopedXREEmbed()
+{
+  Stop();
+  NS_LogTerm();
+}
+
+void
+ScopedXREEmbed::SetAppDir(const nsACString& aPath)
+{
+  bool flag;
+  nsresult rv =
+    XRE_GetFileFromPath(aPath.BeginReading(), getter_AddRefs(mAppDir));
+  if (NS_FAILED(rv) ||
+      NS_FAILED(mAppDir->Exists(&flag)) || !flag) {
+    NS_WARNING("Invalid application directory passed to content process.");
+    mAppDir = nullptr;
+  }
+}
+
+void
+ScopedXREEmbed::Start()
+{
+  std::string path;
+#if defined(OS_WIN)
+  path = WideToUTF8(CommandLine::ForCurrentProcess()->program());
+#elif defined(OS_POSIX)
+  path = CommandLine::ForCurrentProcess()->argv()[0];
+#else
+#  error Sorry
+#endif
+
+  nsCOMPtr<nsIFile> localFile;
+  nsresult rv = XRE_GetBinaryPath(path.c_str(), getter_AddRefs(localFile));
+  if (NS_FAILED(rv))
+    return;
+
+  nsCOMPtr<nsIFile> parent;
+  rv = localFile->GetParent(getter_AddRefs(parent));
+  if (NS_FAILED(rv))
+    return;
+
+  localFile = do_QueryInterface(parent);
+  NS_ENSURE_TRUE_VOID(localFile);
+
+#ifdef OS_MACOSX
+  if (XRE_GetProcessType() == GeckoProcessType_Content) {
+    // We're an XPCOM-using subprocess.  Walk out of
+    // [subprocess].app/Contents/MacOS to the real GRE dir.
+    rv = localFile->GetParent(getter_AddRefs(parent));
+    if (NS_FAILED(rv))
+      return;
+
+    localFile = do_QueryInterface(parent);
+    NS_ENSURE_TRUE_VOID(localFile);
+
+    rv = localFile->GetParent(getter_AddRefs(parent));
+    if (NS_FAILED(rv))
+      return;
+
+    localFile = do_QueryInterface(parent);
+    NS_ENSURE_TRUE_VOID(localFile);
+
+    rv = localFile->GetParent(getter_AddRefs(parent));
+    if (NS_FAILED(rv))
+      return;
+
+    localFile = do_QueryInterface(parent);
+    NS_ENSURE_TRUE_VOID(localFile);
+  }
+#endif
+
+  if (mAppDir)
+    rv = XRE_InitEmbedding2(localFile, mAppDir, nullptr);
+  else
+    rv = XRE_InitEmbedding2(localFile, localFile, nullptr);
+  if (NS_FAILED(rv))
+    return;
+
+  mShouldKillEmbedding = true;
+}
+
+void
+ScopedXREEmbed::Stop()
+{
+  if (mShouldKillEmbedding) {
+    XRE_TermEmbedding();
+    mShouldKillEmbedding = false;
+  }
+}