Add additive animation support for CSS properties perspective-origin and object-position

third_party/WebKit/Source/core/animation/CSSPositionInterpolationType.cpp

Index: third_party/WebKit/Source/core/animation/CSSPositionInterpolationType.cpp
diff --git a/third_party/WebKit/Source/core/animation/CSSPositionInterpolationType.cpp b/third_party/WebKit/Source/core/animation/CSSPositionInterpolationType.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..33987b784bd69bccd0d69ed8dd6a44ee7af2819d
--- /dev/null
+++ b/third_party/WebKit/Source/core/animation/CSSPositionInterpolationType.cpp
@@ -0,0 +1,21 @@
+// Copyright 2016 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 "core/animation/CSSPositionInterpolationType.h"
+
+#include "core/animation/CSSPositionAxisListInterpolationType.h"
+#include "core/animation/ListInterpolationFunctions.h"
+#include "core/css/CSSValuePair.h"
+
+namespace blink {
+
+InterpolationValue CSSPositionInterpolationType::maybeConvertValue(const CSSValue& value, const StyleResolverState&, ConversionCheckers&) const
+{
+    const CSSValuePair& pair = toCSSValuePair(value);
+    return ListInterpolationFunctions::createList(2, [&pair](size_t index) {
+        return CSSPositionAxisListInterpolationType::convertPositionAxisCSSValue(index == 0 ? pair.first() : pair.second());
+    });
+}
+
+} // namespace blink