Deprecate enable-background property

Source/core/css/parser/CSSPropertyParser.cpp

 /*
  * Copyright (C) 2003 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2005 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Nicholas Shanks <webkit@nickshanks.com>
  * Copyright (C) 2008 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2012 Adobe Systems Incorporated. All rights reserved.
  * Copyright (C) 2012 Intel Corporation. All rights reserved.
  *
@@ skipping 7648 matching lines @@
     /* The comment to the right defines all valid value of these
      * properties as defined in SVG 1.1, Appendix N. Property index */
     case CSSPropertyBaselineShift:
     // baseline | super | sub | <percentage> | <length> | inherit
         if (id == CSSValueBaseline || id == CSSValueSub || id == CSSValueSuper)
             validPrimitive = true;
         else
             validPrimitive = validUnit(value, FLength | FPercent, SVGAttributeMode);
         break;
 
-    case CSSPropertyEnableBackground:
-    // accumulate | new [x] [y] [width] [height] | inherit
-        if (id == CSSValueAccumulate) // TODO : new
-            validPrimitive = true;
-        break;
-
     case CSSPropertyClipPath:
     case CSSPropertyFilter:
     case CSSPropertyMarkerStart:
     case CSSPropertyMarkerMid:
     case CSSPropertyMarkerEnd:
     case CSSPropertyMask:
         if (id == CSSValueNone) {
             validPrimitive = true;
         } else if (value->unit() == CSSPrimitiveValue::UnitType::URI) {
             parsedValue = CSSPrimitiveValue::create(value->string, CSSPrimitiveValue::UnitType::URI);
@@ skipping 458 matching lines @@
         }
     }
 
     if (!list->length())
         return nullptr;
 
     return list.release();
 }
 
 } // namespace blink