Revert of Web Animations: Remove AnimationPlayer discarding logic

Source/core/animation/AnimationStackTest.cpp

Index: Source/core/animation/AnimationStackTest.cpp
diff --git a/Source/core/animation/AnimationStackTest.cpp b/Source/core/animation/AnimationStackTest.cpp
index 02c60590eb2f5eae36735397f4ab43212b37be93..b107076f2dd68188a48e0b604d638a6c9038362c 100644
--- a/Source/core/animation/AnimationStackTest.cpp
+++ b/Source/core/animation/AnimationStackTest.cpp
@@ -117,4 +117,38 @@
     EXPECT_TRUE(interpolationValue(result.get(CSSPropertyZIndex))->equals(AnimatableDouble::create(2).get()));
 }
 
+TEST_F(AnimationAnimationStackTest, ForwardsFillDiscarding)
+{
+    play(makeAnimation(makeAnimationEffect(CSSPropertyFontSize, AnimatableDouble::create(1))).get(), 2);
+    play(makeAnimation(makeAnimationEffect(CSSPropertyFontSize, AnimatableDouble::create(2))).get(), 6);
+    play(makeAnimation(makeAnimationEffect(CSSPropertyFontSize, AnimatableDouble::create(3))).get(), 4);
+    document->compositorPendingAnimations().update();
+    WillBeHeapHashMap<CSSPropertyID, RefPtrWillBeMember<Interpolation> > interpolations;
+
+    updateTimeline(11);
+    Heap::collectAllGarbage();
+    interpolations = AnimationStack::activeInterpolations(&element->activeAnimations()->defaultStack(), 0, 0, Animation::DefaultPriority, 0);
+    EXPECT_TRUE(interpolationValue(interpolations.get(CSSPropertyFontSize))->equals(AnimatableDouble::create(3).get()));
+    EXPECT_EQ(3u, effects().size());
+    EXPECT_EQ(1u, interpolations.size());
+
+    updateTimeline(13);
+    Heap::collectAllGarbage();
+    interpolations = AnimationStack::activeInterpolations(&element->activeAnimations()->defaultStack(), 0, 0, Animation::DefaultPriority, 0);
+    EXPECT_TRUE(interpolationValue(interpolations.get(CSSPropertyFontSize))->equals(AnimatableDouble::create(3).get()));
+    EXPECT_EQ(3u, effects().size());
+
+    updateTimeline(15);
+    Heap::collectAllGarbage();
+    interpolations = AnimationStack::activeInterpolations(&element->activeAnimations()->defaultStack(), 0, 0, Animation::DefaultPriority, 0);
+    EXPECT_TRUE(interpolationValue(interpolations.get(CSSPropertyFontSize))->equals(AnimatableDouble::create(3).get()));
+    EXPECT_EQ(2u, effects().size());
+
+    updateTimeline(17);
+    Heap::collectAllGarbage();
+    interpolations = AnimationStack::activeInterpolations(&element->activeAnimations()->defaultStack(), 0, 0, Animation::DefaultPriority, 0);
+    EXPECT_TRUE(interpolationValue(interpolations.get(CSSPropertyFontSize))->equals(AnimatableDouble::create(3).get()));
+    EXPECT_EQ(1u, effects().size());
 }
+
+}