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

Source/core/dom/Element.idl

 /*
  * Copyright (C) 2006, 2007, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2006 Samuel Weinig <sam.weinig@gmail.com>
  *
  * 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 114 matching lines @@
 
     // Mozilla version
     const unsigned short ALLOW_KEYBOARD_INPUT = 1;
     [RuntimeEnabled=Fullscreen, PerWorldBindings, ActivityLogging=ForAllWorlds, MeasureAs=PrefixedElementRequestFullScreen] void webkitRequestFullScreen([Default=Undefined] optional unsigned short flags);
 
     // W3C version
     [RuntimeEnabled=Fullscreen, PerWorldBindings, ActivityLogging=ForAllWorlds, MeasureAs=PrefixedElementRequestFullscreen] void webkitRequestFullscreen();
 
     void webkitRequestPointerLock();
 
-    // CSS Regions API
-    [RuntimeEnabled=CSSRegions, PerWorldBindings] readonly attribute DOMString webkitRegionOverset;
-    [RuntimeEnabled=CSSRegions] sequence<Range> webkitGetRegionFlowRanges();
-
     // Event handler attributes
     attribute EventHandler onbeforecopy;
     attribute EventHandler onbeforecut;
     attribute EventHandler onbeforepaste;
     attribute EventHandler oncopy;
     attribute EventHandler oncut;
     attribute EventHandler onpaste;
     attribute EventHandler onsearch;
     attribute EventHandler onselectstart;
     [RuntimeEnabled=Touch] attribute EventHandler ontouchcancel;
     [RuntimeEnabled=Touch] attribute EventHandler ontouchend;
     [RuntimeEnabled=Touch] attribute EventHandler ontouchmove;
     [RuntimeEnabled=Touch] attribute EventHandler ontouchstart;
     attribute EventHandler onwebkitfullscreenchange;
     attribute EventHandler onwebkitfullscreenerror;
     [PerWorldBindings, ActivityLogging=SetterForIsolatedWorlds] attribute EventHandler onwheel;
 };
 
 Element implements ParentNode;
 Element implements ChildNode;