Support [Replaceable] for screen, pageXOffset, pageYOffset

Source/core/frame/Window.idl

 /*
  * Copyright (C) 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 87 matching lines @@
 
     // CSS Conditional Rules Module
     // http://dev.w3.org/csswg/css-conditional/#the-css-interface
     // FIXME: CSS should be an interface with static members, in which
     // case this getter would not be needed.
     [Replaceable] readonly attribute CSS CSS;
 
     // CSSOM View Module
     // http://dev.w3.org/csswg/cssom-view/#extensions-to-the-window-interface
     [NewObject] MediaQueryList matchMedia(DOMString query);
-    [SameObject] readonly attribute Screen screen;
+    [SameObject, Replaceable] readonly attribute Screen screen;
 
     // browsing context
     // FIXME: The x and y arguments should not be optional. crbug.com/453421
     void moveTo(optional long x, optional long y);
     void moveBy(optional long x, optional long y);
     void resizeTo(optional long x, optional long y);
     void resizeBy(optional long x, optional long y);
 
     // viewport
-    // FIXME: None of the CCSOM View Module attributes should be [Replaceable].
     [Replaceable] readonly attribute long innerWidth;
     [Replaceable] readonly attribute long innerHeight;
 
     // viewport scrolling
     [Replaceable] readonly attribute double scrollX;
-    readonly attribute double pageXOffset;
+    [Replaceable] readonly attribute double pageXOffset;
     [Replaceable] readonly attribute double scrollY;
-    readonly attribute double pageYOffset;
+    [Replaceable] readonly attribute double pageYOffset;
     [RuntimeEnabled=CSSOMSmoothScroll] void scroll(optional ScrollToOptions options);
     void scroll(unrestricted double x, unrestricted double y);
     [RuntimeEnabled=CSSOMSmoothScroll] void scrollTo(optional ScrollToOptions options);
     void scrollTo(unrestricted double x, unrestricted double y);
     [RuntimeEnabled=CSSOMSmoothScroll] void scrollBy(optional ScrollToOptions options);
     void scrollBy(unrestricted double x, unrestricted double y);
 
     // client
     [Replaceable] readonly attribute long screenX;
     [Replaceable] readonly attribute long screenY;
@@ skipping 72 matching lines @@
 // FIXME: make this typedef accurate once enough of http://crbug.com/240176
 // is in place.
 // FIXME: consider putting this typedef in an .idl file containing spec-wide
 // utility type definitions.
 typedef MessagePort Transferable;
 
 Window implements GlobalEventHandlers;
 Window implements WindowBase64;
 Window implements WindowEventHandlers;
 Window implements WindowTimers;