Web Animations API: Interpolate into reference rather than returning new value.

Source/core/animation/InterpolableValue.h

 // 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.
 
 #ifndef InterpolableValue_h
 #define InterpolableValue_h
 
 #include "core/animation/animatable/AnimatableValue.h"
 #include "wtf/OwnPtr.h"
 #include "wtf/PassOwnPtr.h"
 #include "wtf/Vector.h"
 
 namespace blink {
 
 class InterpolableValue : public NoBaseWillBeGarbageCollected<InterpolableValue> {
     DECLARE_EMPTY_VIRTUAL_DESTRUCTOR_WILL_BE_REMOVED(InterpolableValue);
 public:
     virtual bool isNumber() const { return false; }
     virtual bool isBool() const { return false; }
     virtual bool isList() const { return false; }
     virtual bool isAnimatableValue() const { return false; }
 
     virtual PassOwnPtrWillBeRawPtr<InterpolableValue> clone() const = 0;
 
     virtual void trace(Visitor*) { }
 
 private:
-    virtual PassOwnPtrWillBeRawPtr<InterpolableValue> interpolate(const InterpolableValue &to, const double progress) const = 0;
+    virtual void interpolate(const InterpolableValue& to, const double progress, InterpolableValue& result) const = 0;
 
     friend class Interpolation;
 
     // Keep interpolate private, but allow calls within the hierarchy without
     // knowledge of type.
     friend class DeferredLegacyStyleInterpolation;
     friend class InterpolableNumber;
     friend class InterpolableBool;
     friend class InterpolableList;
 };
 
 class InterpolableNumber : public InterpolableValue {
 public:
     static PassOwnPtrWillBeRawPtr<InterpolableNumber> create(double value)
     {
         return adoptPtrWillBeNoop(new InterpolableNumber(value));
     }
 
     virtual bool isNumber() const override final { return true; }
     double value() const { return m_value; }
     virtual PassOwnPtrWillBeRawPtr<InterpolableValue> clone() const override final { return create(m_value); }
 
     virtual void trace(Visitor* visitor) override { InterpolableValue::trace(visitor); }
 
 private:
-    virtual PassOwnPtrWillBeRawPtr<InterpolableValue> interpolate(const InterpolableValue &to, const double progress) const override final;
+    virtual void interpolate(const InterpolableValue& to, const double progress, InterpolableValue& result) const override final;
     double m_value;
 
     explicit InterpolableNumber(double value)
         : m_value(value)
     {
     }
 
 };
 
 class InterpolableBool : public InterpolableValue {
 public:
     static PassOwnPtrWillBeRawPtr<InterpolableBool> create(bool value)
     {
         return adoptPtrWillBeNoop(new InterpolableBool(value));
     }
 
     virtual bool isBool() const override final { return true; }
     bool value() const { return m_value; }
     virtual PassOwnPtrWillBeRawPtr<InterpolableValue> clone() const override final { return create(m_value); }
 
     virtual void trace(Visitor* visitor) override { InterpolableValue::trace(visitor); }
 
 private:
-    virtual PassOwnPtrWillBeRawPtr<InterpolableValue> interpolate(const InterpolableValue &to, const double progress) const override final;
+    virtual void interpolate(const InterpolableValue& to, const double progress, InterpolableValue& result) const override final;
     bool m_value;
 
     explicit InterpolableBool(bool value)
         : m_value(value)
     {
     }
 
 };
 
 class InterpolableList : public InterpolableValue {
@@ skipping 18 matching lines @@
     {
         ASSERT(position < m_size);
         return m_values[position].get();
     }
     size_t length() const { return m_size; }
     virtual PassOwnPtrWillBeRawPtr<InterpolableValue> clone() const override final { return create(*this); }
 
     virtual void trace(Visitor*) override;
 
 private:
-    virtual PassOwnPtrWillBeRawPtr<InterpolableValue> interpolate(const InterpolableValue &other, const double progress) const override final;
+    virtual void interpolate(const InterpolableValue& to, const double progress, InterpolableValue& result) const override final;
     explicit InterpolableList(size_t size)
         : m_size(size)
         , m_values(m_size)
     {
     }
 
     InterpolableList(const InterpolableList& other)
         : m_size(other.m_size)
         , m_values(m_size)
     {
@@ skipping 13 matching lines @@
         return adoptPtrWillBeNoop(new InterpolableAnimatableValue(value));
     }
 
     virtual bool isAnimatableValue() const override final { return true; }
     AnimatableValue* value() const { return m_value.get(); }
     virtual PassOwnPtrWillBeRawPtr<InterpolableValue> clone() const override final { return create(m_value); }
 
     virtual void trace(Visitor*) override;
 
 private:
-    virtual PassOwnPtrWillBeRawPtr<InterpolableValue> interpolate(const InterpolableValue &other, const double progress) const override final;
+    virtual void interpolate(const InterpolableValue &to, const double progress, InterpolableValue& result) const override final;
     RefPtrWillBeMember<AnimatableValue> m_value;
 
     InterpolableAnimatableValue(PassRefPtrWillBeRawPtr<AnimatableValue> value)
         : m_value(value)
     {
     }
 };
 
 DEFINE_TYPE_CASTS(InterpolableNumber, InterpolableValue, value, value->isNumber(), value.isNumber());
 DEFINE_TYPE_CASTS(InterpolableBool, InterpolableValue, value, value->isBool(), value.isBool());
 DEFINE_TYPE_CASTS(InterpolableList, InterpolableValue, value, value->isList(), value.isList());
 DEFINE_TYPE_CASTS(InterpolableAnimatableValue, InterpolableValue, value, value->isAnimatableValue(), value.isAnimatableValue());
 
 }
 
 #endif