Revert of [oilpan]: Remove support for tracing off-heap hashmaps.

Source/core/animation/animatable/AnimatableValueKeyframe.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "config.h"
 #include "core/animation/animatable/AnimatableValueKeyframe.h"
 
 #include "core/animation/LegacyStyleInterpolation.h"
 
 namespace blink {
@@ skipping 20 matching lines @@
     return adoptRefWillBeNoop(new AnimatableValueKeyframe(*this));
 }
 
 PassOwnPtrWillBeRawPtr<Keyframe::PropertySpecificKeyframe> AnimatableValueKeyframe::createPropertySpecificKeyframe(CSSPropertyID property) const
 {
     return adoptPtrWillBeNoop(new PropertySpecificKeyframe(offset(), easing(), propertyValue(property), composite()));
 }
 
 void AnimatableValueKeyframe::trace(Visitor* visitor)
 {
-#if ENABLE(OILPAN)
     visitor->trace(m_propertyValues);
-#endif
     Keyframe::trace(visitor);
 }
 
 AnimatableValueKeyframe::PropertySpecificKeyframe::PropertySpecificKeyframe(double offset, PassRefPtr<TimingFunction> easing, const AnimatableValue* value, AnimationEffect::CompositeOperation op)
     : Keyframe::PropertySpecificKeyframe(offset, easing, op)
     , m_value(const_cast<AnimatableValue*>(value))
 { }
 
 AnimatableValueKeyframe::PropertySpecificKeyframe::PropertySpecificKeyframe(double offset, PassRefPtr<TimingFunction> easing, PassRefPtrWillBeRawPtr<AnimatableValue> value)
     : Keyframe::PropertySpecificKeyframe(offset, easing, AnimationEffect::CompositeReplace)
@@ skipping 19 matching lines @@
     return adoptPtrWillBeNoop(new AnimatableValueKeyframe::PropertySpecificKeyframe(offset, easing, AnimatableValue::neutralValue(), AnimationEffect::CompositeAdd));
 }
 
 void AnimatableValueKeyframe::PropertySpecificKeyframe::trace(Visitor* visitor)
 {
     visitor->trace(m_value);
     Keyframe::PropertySpecificKeyframe::trace(visitor);
 }
 
 }