Implemented additive animations for length

Source/core/animation/InterpolableValue.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/InterpolableValue.h"
 
 namespace blink {
 
 DEFINE_EMPTY_DESTRUCTOR_WILL_BE_REMOVED(InterpolableValue);
 
+bool InterpolableValue::typesMatch(const InterpolableValue& other) const
+{
+    if (isNumber())
+        return other.isNumber();
+    if (isBool())
+        return other.isBool();
+    if (isAnimatableValue())
+        return other.isAnimatableValue();
+    if (!(isList() && other.isList()))
+        return false;
+    const InterpolableList& listA = toInterpolableList(*this);
+    const InterpolableList& listB = toInterpolableList(other);
+    if (listA.length() != listB.length())
+        return false;
+    for (size_t i = 0; i < listA.length(); ++i) {
+        if (!listA.get(i)->typesMatch(*listB.get(i)))
+            return false;
+    }
+    return true;
+}
+
 void InterpolableNumber::interpolate(const InterpolableValue &to, const double progress, InterpolableValue& result) const
 {
     const InterpolableNumber& toNumber = toInterpolableNumber(to);
     InterpolableNumber& resultNumber = toInterpolableNumber(result);
 
     if (progress == 0)
         resultNumber.m_value = m_value;
     else if (progress == 1)
         resultNumber.m_value = toNumber.m_value;
     else
@@ skipping 95 matching lines @@
     resultValue.m_value = AnimatableValue::interpolate(m_value.get(), toValue.m_value.get(), progress);
 }
 
 void InterpolableAnimatableValue::trace(Visitor* visitor)
 {
     visitor->trace(m_value);
     InterpolableValue::trace(visitor);
 }
 
 }