Implemented additive animations for length

Source/core/animation/InterpolationPipelineStage.h

Index: Source/core/animation/InterpolationPipelineStage.h
diff --git a/Source/core/animation/InterpolationPipelineStage.h b/Source/core/animation/InterpolationPipelineStage.h
new file mode 100644
index 0000000000000000000000000000000000000000..062ae81047aeba3f6a3473c3ea7560836867e747
--- /dev/null
+++ b/Source/core/animation/InterpolationPipelineStage.h
@@ -0,0 +1,64 @@
+// Copyright 2015 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 InterpolationPipelineStage_h
+#define InterpolationPipelineStage_h
+
+#include "core/CSSPropertyNames.h"
+#include "core/animation/Interpolation.h"
+#include "platform/heap/Handle.h"
+
+namespace blink {
+
+class InterpolationPipelineStage : public RefCountedWillBeGarbageCollected<InterpolationPipelineStage> {
+public:
+    static PassRefPtrWillBeRawPtr<InterpolationPipelineStage> create(PassRefPtrWillBeRawPtr<Interpolation> interpolation)
+    {
+        return adoptRefWillBeNoop(new InterpolationPipelineStage(interpolation));
+    }
+
+    RefPtrWillBeRawPtr<Interpolation> interpolation() const
+    {
+        return m_interpolation;
+    }
+
+    RefPtrWillBeRawPtr<InterpolationPipelineStage> next() const
+    {
+        return m_next;
+    }
+
+    void setNext(RefPtrWillBeRawPtr<InterpolationPipelineStage> next)

[alancutter (OOO until 2018), 2015/02/12 05:55:45]

This should be a PassRefPtr.

+    {
+        if (next) {
+            m_next = next;
+        } else {
+            RefPtrWillBeRawPtr<InterpolationPipelineStage> a = nullptr;
+            m_next = a;
+        }

[alancutter (OOO until 2018), 2015/02/12 05:55:45]

Why not just set m_next = next?

+    }
+
+    void trace(Visitor* visitor)
+    {
+        m_interpolation->trace(visitor);
+        m_next->trace(visitor);
+    }
+
+    ~InterpolationPipelineStage()
+    {
+    }

[alancutter (OOO until 2018), 2015/02/12 05:55:45]

This is unneeded.

+private:
+    InterpolationPipelineStage(PassRefPtrWillBeRawPtr<Interpolation> interpolation)
+        : m_interpolation(interpolation)
+        , m_next(nullptr)
+    {
+    }
+
+    RefPtrWillBeMember<Interpolation> m_interpolation;
+
+    RefPtrWillBeMember<InterpolationPipelineStage> m_next;
+};
+
+} // namespace blink
+
+#endif // InterpolationPipelineStage_h