Do not treat '0' as 'none' for font-size-adjust

Source/core/animation/css/CSSAnimatableValueFactory.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 371 matching lines @@
         return createFromColor(property, style);
     case CSSPropertyFloodOpacity:
         return createFromDouble(style.floodOpacity());
     case CSSPropertyFontSize:
         // Must pass a specified size to setFontSize if Text Autosizing is enabled, but a computed size
         // if text zoom is enabled (if neither is enabled it's irrelevant as they're probably the same).
         // FIXME: Should we introduce an option to pass the computed font size here, allowing consumers to
         // enable text zoom rather than Text Autosizing? See http://crbug.com/227545.
         return createFromDouble(style.specifiedFontSize());
     case CSSPropertyFontSizeAdjust:
-        return createFromDouble(style.fontSizeAdjust(), AnimatableDouble::InterpolationIsNonContinuousWithZero);
+        return style.hasFontSizeAdjust() ? createFromDouble(style.fontSizeAdjust()) : AnimatableUnknown::create(CSSValueNone);
     case CSSPropertyFontStretch:
         return createFromFontStretch(style.fontStretch());
     case CSSPropertyFontWeight:
         return createFromFontWeight(style.fontWeight());
     case CSSPropertyHeight:
         return createFromLength(style.height(), style);
     case CSSPropertyLightingColor:
         return createFromColor(property, style);
     case CSSPropertyListStyleImage:
         return createFromStyleImage(style.listStyleImage());
@@ skipping 153 matching lines @@
     case CSSPropertyZIndex:
         return createFromDouble(style.zIndex());
     default:
         ASSERT_NOT_REACHED();
         // This return value is to avoid a release crash if possible.
         return AnimatableUnknown::create(nullptr);
     }
 }
 
 } // namespace blink