Web Animations: Remove legacy animations engine.

Source/core/animation/css/CSSAnimations.cpp

 /*
  * Copyright (C) 2013 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 882 matching lines @@
     case CSSPropertyWebkitTransform:
     case CSSPropertyWebkitTransformOriginX:
     case CSSPropertyWebkitTransformOriginY:
     case CSSPropertyWebkitTransformOriginZ:
     case CSSPropertyWidows:
     case CSSPropertyWidth:
     case CSSPropertyWordSpacing:
     case CSSPropertyZIndex:
     case CSSPropertyZoom:
         return true;
-    // FIXME: Shorthands should not be present in this list, but
-    // CSSPropertyAnimation implements animation of these shorthands
-    // directly and makes use of this method.
-    case CSSPropertyFlex:
-        return !RuntimeEnabledFeatures::webAnimationsCSSEnabled();
     default:
         return false;
     }
 }
 
 const StylePropertyShorthand& CSSAnimations::animatableProperties()
 {
     DEFINE_STATIC_LOCAL(Vector<CSSPropertyID>, properties, ());
     DEFINE_STATIC_LOCAL(StylePropertyShorthand, propertyShorthand, ());
     if (properties.isEmpty()) {
         for (int i = firstCSSProperty; i < lastCSSProperty; ++i) {
             CSSPropertyID id = convertToCSSPropertyID(i);
             if (isAnimatableProperty(id))
                 properties.append(id);
         }
         propertyShorthand = StylePropertyShorthand(CSSPropertyInvalid, properties.begin(), properties.size());
     }
     return propertyShorthand;
 }
 
 } // namespace WebCore