Add a runtime flag for the column-fill property.

Source/core/css/ComputedStyleCSSValueMapping.cpp

 /*
  * Copyright (C) 2004 Zack Rusin <zack@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alexey Proskuryakov <ap@webkit.org>
  * Copyright (C) 2007 Nicholas Shanks <webkit@nickshanks.com>
  * Copyright (C) 2011 Sencha, Inc. All rights reserved.
  * Copyright (C) 2015 Google Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
@@ skipping 1478 matching lines @@
         return cssValuePool().createValue(style.clear());
     case CSSPropertyColor:
         return cssValuePool().createColorValue(allowVisitedStyle ? style.visitedDependentColor(CSSPropertyColor).rgb() : style.color().rgb());
     case CSSPropertyWebkitPrintColorAdjust:
         return cssValuePool().createValue(style.printColorAdjust());
     case CSSPropertyWebkitColumnCount:
         if (style.hasAutoColumnCount())
             return cssValuePool().createIdentifierValue(CSSValueAuto);
         return cssValuePool().createValue(style.columnCount(), CSSPrimitiveValue::CSS_NUMBER);
     case CSSPropertyColumnFill:
-        ASSERT(RuntimeEnabledFeatures::regionBasedColumnsEnabled());
+        ASSERT(RuntimeEnabledFeatures::columnFillEnabled());
         return cssValuePool().createValue(style.columnFill());
     case CSSPropertyWebkitColumnGap:
         if (style.hasNormalColumnGap())
             return cssValuePool().createIdentifierValue(CSSValueNormal);
         return zoomAdjustedPixelValue(style.columnGap(), style);
     case CSSPropertyWebkitColumnRuleColor:
         return allowVisitedStyle ? cssValuePool().createColorValue(style.visitedDependentColor(CSSPropertyOutlineColor).rgb()) : currentColorOrValidColor(style, style.columnRuleColor());
     case CSSPropertyWebkitColumnRuleStyle:
         return cssValuePool().createValue(style.columnRuleStyle());
     case CSSPropertyWebkitColumnRuleWidth:
@@ skipping 1071 matching lines @@
     case CSSPropertyAll:
         return nullptr;
     default:
         break;
     }
     ASSERT_NOT_REACHED();
     return nullptr;
 }
 
 }