Web Animations: Add Interpolation class.

Source/core/animation/Interpolation.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/Interpolation.h"
+
+namespace WebCore {
+
+namespace {
+
+bool typesMatch(const InterpolableValue* start, const InterpolableValue* end)
+{
+    if (start->isNumber())
+        return end->isNumber();
+    if (start->isBool())
+        return end->isBool();
+    if (!(start->isList() && end->isList()))
+        return false;
+    const InterpolableList* startList = toInterpolableList(start);
+    const InterpolableList* endList = toInterpolableList(end);
+    if (startList->length() != endList->length())
+        return false;
+    for (size_t i = 0; i < startList->length(); ++i) {
+        if (!typesMatch(startList->get(i), endList->get(i)))
+            return false;
+    }
+    return true;
+}
+
+}
+
+Interpolation::Interpolation(PassOwnPtr<InterpolableValue> start, PassOwnPtr<InterpolableValue> end)
+    : m_start(start)
+    , m_end(end)
+    , m_cachedFraction(0)
+    , m_cachedValue(m_start->clone())
+{
+    RELEASE_ASSERT(typesMatch(m_start.get(), m_end.get()));
+}
+
+void Interpolation::interpolate(double fraction) const
+{
+    if (m_cachedFraction != fraction) {
+        m_cachedValue = m_start->interpolate(*m_end, fraction);
+        m_cachedFraction = fraction;
+    }
+}
+
+}