Remove CSS regions support, keeping a bare minimum to support "region-based" multicol.

Source/core/dom/Document.idl

 /*
  * Copyright (C) 2006, 2007, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2006, 2007 Samuel Weinig <sam@webkit.org>
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 139 matching lines @@
 
     readonly attribute DOMString compatMode;
 
     // NodeSelector - Selector API
     [RaisesException] Element querySelector(DOMString selectors);
     [RaisesException] NodeList querySelectorAll(DOMString selectors);
 
     void webkitExitPointerLock();
     readonly attribute Element webkitPointerLockElement;
 
-    [RuntimeEnabled=CSSRegions] WebKitNamedFlowCollection webkitGetNamedFlows();
-
     // Event handler attributes
     attribute EventHandler onbeforecopy;
     attribute EventHandler onbeforecut;
     attribute EventHandler onbeforepaste;
     attribute EventHandler oncopy;
     attribute EventHandler oncut;
     attribute EventHandler onpaste;
     attribute EventHandler onreadystatechange;
     attribute EventHandler onsearch;
     [RuntimeEnabled=ExperimentalContentSecurityPolicyFeatures] attribute EventHandler onsecuritypolicyviolation;
@@ skipping 36 matching lines @@
     // document in the console. It's possible http://crbug.com/43394 will resolve this.
     [MeasureAs=PrefixedPageVisibility, ImplementedAs=visibilityState] readonly attribute DOMString webkitVisibilityState;
     [MeasureAs=PrefixedPageVisibility, ImplementedAs=hidden] readonly attribute boolean webkitHidden;
 
     readonly attribute HTMLScriptElement currentScript;
 };
 
 Document implements GlobalEventHandlers;
 Document implements ParentNode;