--- a/dom/base/nsGlobalWindowInner.h
+++ b/dom/base/nsGlobalWindowInner.h
@@ -26,17 +26,16 @@
 // Interfaces Needed
 #include "nsIBrowserDOMWindow.h"
 #include "nsIDOMEventTarget.h"
 #include "nsIInterfaceRequestor.h"
 #include "nsIDOMChromeWindow.h"
 #include "nsIScriptGlobalObject.h"
 #include "nsIScriptObjectPrincipal.h"
 #include "nsITimer.h"
-#include "nsIDOMModalContentWindow.h"
 #include "mozilla/EventListenerManager.h"
 #include "nsIPrincipal.h"
 #include "nsSize.h"
 #include "mozilla/FlushType.h"
 #include "prclist.h"
 #include "mozilla/dom/DOMPrefs.h"
 #include "mozilla/dom/BindingDeclarations.h"
 #include "mozilla/dom/StorageEvent.h"

--- a/dom/base/nsGlobalWindowOuter.h
+++ b/dom/base/nsGlobalWindowOuter.h
@@ -26,17 +26,16 @@
 // Interfaces Needed
 #include "nsIBrowserDOMWindow.h"
 #include "nsIDOMEventTarget.h"
 #include "nsIInterfaceRequestor.h"
 #include "nsIDOMChromeWindow.h"
 #include "nsIScriptGlobalObject.h"
 #include "nsIScriptObjectPrincipal.h"
 #include "nsITimer.h"
-#include "nsIDOMModalContentWindow.h"
 #include "mozilla/EventListenerManager.h"
 #include "nsIPrincipal.h"
 #include "nsSize.h"
 #include "mozilla/FlushType.h"
 #include "prclist.h"
 #include "mozilla/dom/BindingDeclarations.h"
 #include "mozilla/dom/StorageEvent.h"
 #include "mozilla/dom/StorageEventBinding.h"

--- a/dom/interfaces/base/moz.build
+++ b/dom/interfaces/base/moz.build
@@ -16,17 +16,16 @@ XPIDL_SOURCES += [
     'nsIContentProcess.idl',
     'nsIContentURIGrouper.idl',
     'nsIDOMChromeWindow.idl',
     'nsIDOMClientRect.idl',
     'nsIDOMClientRectList.idl',
     'nsIDOMConstructor.idl',
     'nsIDOMGlobalPropertyInitializer.idl',
     'nsIDOMHistory.idl',
-    'nsIDOMModalContentWindow.idl',
     'nsIDOMScreen.idl',
     'nsIDOMWindow.idl',
     'nsIDOMWindowCollection.idl',
     'nsIDOMWindowUtils.idl',
     'nsIFocusManager.idl',
     'nsIIdleObserver.idl',
     'nsIQueryContentEventResult.idl',
     'nsIRemoteBrowser.idl',

deleted file mode 100644
--- a/dom/interfaces/base/nsIDOMModalContentWindow.idl
+++ /dev/null
@@ -1,26 +0,0 @@
-/* -*- Mode: IDL; tab-width: 2; 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/. */
-
-#include "nsISupports.idl"
-
-interface nsIVariant;
-interface nsIArray;
-
-[scriptable, uuid(3f4cb2d0-5f7e-44a9-9f4f-370945f8db08)]
-interface nsIDOMModalContentWindow : nsISupports
-{
-  /**
-   * Readonly attribute containing an arbitrary JS value passed by the
-   * code that opened the modal content window. A security check is
-   * performed at access time, per spec.
-   */
-  readonly attribute nsIVariant            dialogArguments;
-
-  /**
-   * The return value that will be returned to the function that
-   * opened the modal content window.
-   */
-  attribute nsIVariant                   returnValue;
-};

--- a/toolkit/components/windowwatcher/nsWindowWatcher.cpp
+++ b/toolkit/components/windowwatcher/nsWindowWatcher.cpp
@@ -27,17 +27,16 @@
 #include "nsIDocShellLoadInfo.h"
 #include "nsIDocShellTreeItem.h"
 #include "nsIDocShellTreeOwner.h"
 #include "nsIDocumentLoader.h"
 #include "nsIDocument.h"
 #include "nsIDOMDocument.h"
 #include "nsIDOMWindow.h"
 #include "nsIDOMChromeWindow.h"
-#include "nsIDOMModalContentWindow.h"
 #include "nsIPrompt.h"
 #include "nsIScriptObjectPrincipal.h"
 #include "nsIScreen.h"
 #include "nsIScreenManager.h"
 #include "nsIScriptContext.h"
 #include "nsIObserverService.h"
 #include "nsIScriptSecurityManager.h"
 #include "nsXPCOM.h"