Web Animations API: Constructing an Animation from a partial keyframe throws a JS exception

Source/core/animation/KeyframeEffectModel.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 226 matching lines @@
                 applyTo = std::numeric_limits<double>::infinity();
             m_interpolationEffect->addInterpolation(
                 LegacyStyleInterpolation::create(
                     AnimatableValue::takeConstRef(start),
                     AnimatableValue::takeConstRef(end), iter->key),
                 keyframes[i]->easing(), keyframes[i]->offset(), keyframes[i + 1]->offset(), applyFrom, applyTo);
         }
     }
 }
 
+bool KeyframeEffectModel::isReplaceOnly()
+{
+    ensureKeyframeGroups();
+    for (KeyframeGroupMap::iterator iter = m_keyframeGroups->begin(); iter != m_keyframeGroups->end(); ++iter) {
+        const PropertySpecificKeyframeVector& keyframeVector = iter->value->keyframes();
+        for (size_t i = 0; i < keyframeVector.size(); ++i) {
+            if (keyframeVector[i]->composite() != AnimationEffect::CompositeReplace)
+                return false;
+        }
+    }
+    return true;
+}
+
 KeyframeEffectModel::PropertySpecificKeyframe::PropertySpecificKeyframe(double offset, PassRefPtr<TimingFunction> easing, const AnimatableValue* value, CompositeOperation composite)
     : m_offset(offset)
     , m_easing(easing)
+    , m_composite(composite)
 {
     m_value = AnimatableValue::takeConstRef(value);
 }
 
-KeyframeEffectModel::PropertySpecificKeyframe::PropertySpecificKeyframe(double offset, PassRefPtr<TimingFunction> easing, PassRefPtr<AnimatableValue> value)
+KeyframeEffectModel::PropertySpecificKeyframe::PropertySpecificKeyframe(double offset, PassRefPtr<TimingFunction> easing, PassRefPtr<AnimatableValue> value, CompositeOperation composite)
     : m_offset(offset)
     , m_easing(easing)
     , m_value(value)
+    , m_composite(composite)
 {
     ASSERT(!isNull(m_offset));
 }
 
 PassOwnPtr<KeyframeEffectModel::PropertySpecificKeyframe> KeyframeEffectModel::PropertySpecificKeyframe::cloneWithOffset(double offset) const
 {
-    return adoptPtr(new PropertySpecificKeyframe(offset, m_easing, m_value));
+    return adoptPtr(new PropertySpecificKeyframe(offset, m_easing, m_value, m_composite));
 }
 
 
 void KeyframeEffectModel::PropertySpecificKeyframeGroup::appendKeyframe(PassOwnPtr<PropertySpecificKeyframe> keyframe)
 {
     ASSERT(m_keyframes.isEmpty() || m_keyframes.last()->offset() <= keyframe->offset());
     m_keyframes.append(keyframe);
 }
 
 void KeyframeEffectModel::PropertySpecificKeyframeGroup::removeRedundantKeyframes()
@@ skipping 23 matching lines @@
     if (m_keyframes.last()->offset() != 1.0)
         appendKeyframe(adoptPtr(new PropertySpecificKeyframe(1, nullptr, AnimatableValue::neutralValue(), CompositeAdd)));
 }
 
 void KeyframeEffectModel::trace(Visitor* visitor)
 {
     visitor->trace(m_keyframes);
 }
 
 } // namespace