Web Animations API: Implement step-middle and steps(x, middle) timing functions.

Source/core/animation/CompositorAnimationsTest.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:
  *
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  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 65 matching lines @@
     KeyframeEffectModel::KeyframeVector m_keyframeVector5;
     RefPtr<KeyframeEffectModel> m_keyframeAnimationEffect5;
 
     virtual void SetUp()
     {
         AnimationCompositorAnimationsTestBase::SetUp();
 
         m_linearTimingFunction = LinearTimingFunction::create();
         m_cubicEaseTimingFunction = CubicBezierTimingFunction::preset(CubicBezierTimingFunction::Ease);
         m_cubicCustomTimingFunction = CubicBezierTimingFunction::create(1, 2, 3, 4);
-        m_stepTimingFunction = StepsTimingFunction::create(1, false);
+        m_stepTimingFunction = StepsTimingFunction::create(1, StepsTimingFunction::StepAtEnd);
 
         m_timing = createCompositableTiming();
         m_compositorTiming = CompositorAnimationsImpl::CompositorTiming();
         // Make sure the CompositableTiming is really compositable, otherwise
         // most other tests will fail.
         ASSERT(convertTimingForCompositor(m_timing, m_compositorTiming));
 
         m_keyframeVector2 = createCompositableFloatKeyframeVector(2);
         m_keyframeAnimationEffect2 = KeyframeEffectModel::create(m_keyframeVector2);
 
@@ skipping 940 matching lines @@
     // Go!
     setCompositorForTesting(mockCompositor);
     Vector<OwnPtr<blink::WebAnimation> > result;
     getAnimationOnCompositor(m_timing, *effect.get(), result);
     EXPECT_EQ(1U, result.size());
     result[0].clear();
 }
 
 
 } // namespace WebCore