diff -r 000000000000 -r 6474c204b198 hal/WindowIdentifier.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/hal/WindowIdentifier.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,82 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set sw=2 ts=8 et ft=cpp : */
+/* 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/ContentChild.h"
+#include "WindowIdentifier.h"
+#include "nsPIDOMWindow.h"
+
+namespace mozilla {
+namespace hal {
+
+WindowIdentifier::WindowIdentifier()
+  : mWindow(nullptr)
+  , mIsEmpty(true)
+{
+}
+
+WindowIdentifier::WindowIdentifier(nsIDOMWindow *window)
+  : mWindow(window)
+  , mIsEmpty(false)
+{
+  mID.AppendElement(GetWindowID());
+}
+
+WindowIdentifier::WindowIdentifier(const InfallibleTArray<uint64_t> &id, nsIDOMWindow *window)
+  : mID(id)
+  , mWindow(window)
+  , mIsEmpty(false)
+{
+  mID.AppendElement(GetWindowID());
+}
+
+WindowIdentifier::WindowIdentifier(const WindowIdentifier &other)
+  : mID(other.mID)
+  , mWindow(other.mWindow)
+  , mIsEmpty(other.mIsEmpty)
+{
+}
+
+const InfallibleTArray<uint64_t>&
+WindowIdentifier::AsArray() const
+{
+  MOZ_ASSERT(!mIsEmpty);
+  return mID;
+}
+
+bool
+WindowIdentifier::HasTraveledThroughIPC() const
+{
+  MOZ_ASSERT(!mIsEmpty);
+  return mID.Length() >= 2;
+}
+
+void
+WindowIdentifier::AppendProcessID()
+{
+  MOZ_ASSERT(!mIsEmpty);
+  mID.AppendElement(dom::ContentChild::GetSingleton()->GetID());
+}
+
+uint64_t
+WindowIdentifier::GetWindowID() const
+{
+  MOZ_ASSERT(!mIsEmpty);
+  nsCOMPtr<nsPIDOMWindow> pidomWindow = do_QueryInterface(mWindow);
+  if (!pidomWindow) {
+    return UINT64_MAX;
+  }
+  return pidomWindow->WindowID();
+}
+
+nsIDOMWindow*
+WindowIdentifier::GetWindow() const
+{
+  MOZ_ASSERT(!mIsEmpty);
+  return mWindow;
+}
+
+} // namespace hal
+} // namespace mozilla