Web Animations CSS: Assert underlying value is not used

Source/core/animation/KeyframeAnimationEffect.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 26 matching lines @@
 namespace {
 
 using namespace WebCore;
 
 class ReplaceCompositableValue : public AnimationEffect::CompositableValue {
 public:
     static PassRefPtr<ReplaceCompositableValue> create(const AnimatableValue* value)
     {
         return adoptRef(new ReplaceCompositableValue(value));
     }
+    virtual bool dependsOnUnderlyingValue() const
+    {
+        return false;
+    }
     virtual PassRefPtr<AnimatableValue> compositeOnto(const AnimatableValue* underlyingValue) const
     {
         return PassRefPtr<AnimatableValue>(m_value);
     }
 private:
     ReplaceCompositableValue(const AnimatableValue* value)
         : m_value(const_cast<AnimatableValue*>(value))
     {
     }
     RefPtr<AnimatableValue> m_value;
 };
 
 class AddCompositableValue : public AnimationEffect::CompositableValue {
 public:
     static PassRefPtr<AddCompositableValue> create(const AnimatableValue* value)
     {
         return adoptRef(new AddCompositableValue(value));
     }
+    virtual bool dependsOnUnderlyingValue() const
+    {
+        return true;
+    }
     virtual PassRefPtr<AnimatableValue> compositeOnto(const AnimatableValue* underlyingValue) const
     {
         return AnimatableValue::add(underlyingValue, m_value.get());
     }
 private:
     AddCompositableValue(const AnimatableValue* value)
         : m_value(const_cast<AnimatableValue*>(value))
     {
     }
     RefPtr<AnimatableValue> m_value;
 };
 
 class BlendedCompositableValue : public AnimationEffect::CompositableValue {
 public:
     static PassRefPtr<BlendedCompositableValue> create(const AnimationEffect::CompositableValue* before, const AnimationEffect::CompositableValue* after, double fraction)
     {
         return adoptRef(new BlendedCompositableValue(before, after, fraction));
     }
+    virtual bool dependsOnUnderlyingValue() const
+    {
+        return m_dependsOnUnderlyingValue;
+    }
     virtual PassRefPtr<AnimatableValue> compositeOnto(const AnimatableValue* underlyingValue) const
     {
         return AnimatableValue::interpolate(m_before->compositeOnto(underlyingValue).get(), m_after->compositeOnto(underlyingValue).get(), m_fraction);
     }
 private:
     BlendedCompositableValue(const AnimationEffect::CompositableValue* before, const AnimationEffect::CompositableValue* after, double fraction)
         : m_before(const_cast<AnimationEffect::CompositableValue*>(before))
         , m_after(const_cast<AnimationEffect::CompositableValue*>(after))
         , m_fraction(fraction)
+        , m_dependsOnUnderlyingValue(before->dependsOnUnderlyingValue() || after->dependsOnUnderlyingValue())
     { }
     RefPtr<AnimationEffect::CompositableValue> m_before;
     RefPtr<AnimationEffect::CompositableValue> m_after;
     double m_fraction;
+    bool m_dependsOnUnderlyingValue;
 };
 
 } // namespace
 
 
 namespace WebCore {
 
 Keyframe::Keyframe()
     : m_offset(std::numeric_limits<double>::quiet_NaN())
     , m_composite(AnimationEffect::CompositeReplace)
@@ skipping 195 matching lines @@
 
     if ((*before)->offset() == offset)
         return const_cast<CompositableValue*>((*before)->value());
     if ((*after)->offset() == offset)
         return const_cast<CompositableValue*>((*after)->value());
     return BlendedCompositableValue::create((*before)->value(), (*after)->value(),
         (offset - (*before)->offset()) / ((*after)->offset() - (*before)->offset()));
 }
 
 } // namespace