Web Animations: define distance for AnimatableColor

Source/core/animation/AnimatableDoubleTest.cpp

Index: Source/core/animation/AnimatableDoubleTest.cpp
diff --git a/Source/core/animation/AnimatableDoubleTest.cpp b/Source/core/animation/AnimatableDoubleTest.cpp
index d6f9a5983e260fe0bcfac7005aedc47720391de8..973cd43ff8432581c8983012dddafd36224b3016 100644
--- a/Source/core/animation/AnimatableDoubleTest.cpp
+++ b/Source/core/animation/AnimatableDoubleTest.cpp
@@ -88,4 +88,15 @@ TEST(AnimationAnimatableDoubleTest, Add)
     EXPECT_EQ(30, toAnimatableDouble(AnimatableValue::add(AnimatableDouble::create(30).get(), AnimatableDouble::create(0).get()).get())->toDouble());
 }
 
+TEST(AnimationAnimatableDoubleTest, Distance)
+{
+    RefPtrWillBeRawPtr<AnimatableDouble> first = AnimatableDouble::create(-1.5);
+    RefPtrWillBeRawPtr<AnimatableDouble> second = AnimatableDouble::create(2.25);
+    RefPtrWillBeRawPtr<AnimatableDouble> third = AnimatableDouble::create(3);
+
+    EXPECT_DOUBLE_EQ(3.75, AnimatableValue::distance(first.get(), second.get()));
+    EXPECT_DOUBLE_EQ(0.75, AnimatableValue::distance(second.get(), third.get()));
+    EXPECT_DOUBLE_EQ(4.5, AnimatableValue::distance(third.get(), first.get()));
+}
+
 }