Web Animations: Sort Animations in the AnimationStack

Source/core/core.gypi

 {
     'variables': {
         # Files for which bindings (.cpp and .h files) will be generated
         'core_idl_files': [
             'animation/Animation.idl',
             'animation/AnimationPlayer.idl',
             'animation/TimedItem.idl',
             'animation/Timeline.idl',
             'animation/Timing.idl',
             'clipboard/DataTransfer.idl',
@@ skipping 3254 matching lines @@
             'animation/AnimatableDoubleTest.cpp',
             'animation/AnimatableLengthTest.cpp',
             'animation/AnimatableNeutralTest.cpp',
             'animation/AnimatableStrokeDasharrayListTest.cpp',
             'animation/AnimatableUnknownTest.cpp',
             'animation/AnimatableValueTestHelper.cpp',
             'animation/AnimatableValueTestHelper.h',
             'animation/AnimatableValueTestHelperTest.cpp',
             'animation/AnimationClockTest.cpp',
             'animation/AnimationHelpersTest.cpp',
+            'animation/AnimationStackTest.cpp',
             'animation/AnimationTest.cpp',
             'animation/AnimationTestHelper.cpp',
             'animation/AnimationTestHelper.h',
             'animation/AnimationTranslationUtilTest.cpp',
             'animation/CompositorAnimationsTest.cpp',
             'animation/CompositorAnimationsTestHelper.h',
             'animation/CompositorAnimationsTimingFunctionReverserTest.cpp',
             'animation/DocumentTimelineTest.cpp',
             'animation/InterpolableValueTest.cpp',
             'animation/InterpolationEffectTest.cpp',
@@ skipping 40 matching lines @@
             'html/track/vtt/BufferedLineReaderTest.cpp',
             'html/track/vtt/VTTScannerTest.cpp',
             'rendering/RenderOverflowTest.cpp',
             'rendering/shapes/BoxShapeTest.cpp',
             'testing/UnitTestHelpers.cpp',
             'testing/UnitTestHelpers.h',
             'xml/parser/SharedBufferReaderTest.cpp',
         ],
     }
 }