Web Animations: define distance for AnimatableColor

Source/core/animation/AnimatableDouble.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 16 matching lines @@
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #include "config.h"
 #include "core/animation/AnimatableDouble.h"
 
 #include "core/css/CSSPrimitiveValue.h"
 #include "core/css/CSSValuePool.h"
 #include "platform/animation/AnimationUtilities.h"
+#include <math.h>
 
 namespace WebCore {
 
 PassRefPtrWillBeRawPtr<CSSValue> AnimatableDouble::toCSSValue() const
 {
     return cssValuePool().createValue(m_number, CSSPrimitiveValue::CSS_NUMBER);
 }
 
 bool AnimatableDouble::usesDefaultInterpolationWith(const AnimatableValue* value) const
 {
@@ skipping 20 matching lines @@
         return takeConstRef(this);
 
     return AnimatableDouble::create(m_number + other->m_number);
 }
 
 bool AnimatableDouble::equalTo(const AnimatableValue* value) const
 {
     return m_number == toAnimatableDouble(value)->m_number;
 }
 
+double AnimatableDouble::distanceTo(const AnimatableValue* value) const
+{
+    const AnimatableDouble* other = toAnimatableDouble(value);
+    return fabs(m_number - other->m_number);
+}
+
 } // namespace WebCore