Web Animations: Enable additive animations in experimental

Source/core/animation/EffectInput.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 223 matching lines @@
             lastOffset = offset;
 
             keyframe->setOffset(offset);
         }
         keyframes.append(keyframe);
 
         String compositeString;
         DictionaryHelper::get(keyframeDictionary, "composite", compositeString);
         if (compositeString == "add")
             keyframe->setComposite(EffectModel::CompositeAdd);
+        // TODO(alancutter): Support "accumulate" keyframe composition.
 
         String timingFunctionString;
         if (DictionaryHelper::get(keyframeDictionary, "easing", timingFunctionString)) {
             if (RefPtr<TimingFunction> timingFunction = AnimationInputHelpers::parseTimingFunction(timingFunctionString))
                 keyframe->setEasing(timingFunction);
         }
 
         Vector<String> keyframeProperties;
         keyframeDictionary.getPropertyNames(keyframeProperties);
         for (const auto& property : keyframeProperties) {
@@ skipping 16 matching lines @@
 
             SVGElement* svgElement = toSVGElement(element);
             const QualifiedName* qualifiedName = supportedSVGAttribute(property, svgElement);
 
             if (qualifiedName)
                 keyframe->setPropertyValue(*qualifiedName, value, svgElement);
         }
     }
 
     StringKeyframeEffectModel* keyframeEffectModel = StringKeyframeEffectModel::create(keyframes);
-    if (keyframeEffectModel->hasSyntheticKeyframes()) {
-        exceptionState.throwDOMException(NotSupportedError, "Partial keyframes are not supported.");
-        return nullptr;
-    }
-    if (!keyframeEffectModel->isReplaceOnly()) {
-        exceptionState.throwDOMException(NotSupportedError, "Additive animations are not supported.");
-        return nullptr;
+    if (!RuntimeEnabledFeatures::additiveAnimationsEnabled()) {
+        if (keyframeEffectModel->hasSyntheticKeyframes()) {
+            exceptionState.throwDOMException(NotSupportedError, "Partial keyframes are not supported.");
+            return nullptr;
+        }
+        if (!keyframeEffectModel->isReplaceOnly()) {
+            exceptionState.throwDOMException(NotSupportedError, "Additive animations are not supported.");
+            return nullptr;
+        }
     }
     keyframeEffectModel->forceConversionsToAnimatableValues(*element, element->computedStyle());
 
     return keyframeEffectModel;
 }
 
-EffectModel* EffectInput::convert(Element* element, const EffectModelOrDictionarySequence& effectInput, ExceptionState& exceptionState)
+EffectModel* EffectInput::convert(Element* element, const EffectModelOrDictionarySequenceOrDictionary& effectInput, ExceptionState& exceptionState)
 {
     if (effectInput.isEffectModel())
         return effectInput.getAsEffectModel();
     if (effectInput.isDictionarySequence())
         return convert(element, effectInput.getAsDictionarySequence(), exceptionState);
+    if (effectInput.isDictionary()) {
+        Vector<Dictionary> keyframes;
+        keyframes.append(effectInput.getAsDictionary());
+        return convert(element, keyframes, exceptionState);
+    }
     return nullptr;
 }
 
 } // namespace blink