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

Source/core/animation/TimedItemCalculationsTest.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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  *     * Redistributions in binary form must reproduce the above
@@ skipping 166 matching lines @@
     // calculateTransformedTime(currentIteration, iterationDuration, iterationTime, timing)
 
     // Iteration time is null
     EXPECT_TRUE(isNull(calculateTransformedTime(1, 2, nullValue(), timing)));
 
     // PlaybackDirectionForwards
     EXPECT_EQ(12, calculateTransformedTime(0, 20, 12, timing));
     EXPECT_EQ(12, calculateTransformedTime(1, 20, 12, timing));
 
     // PlaybackDirectionForwards with timing function
-    timing.timingFunction = StepsTimingFunction::create(4, false /* stepAtStart */);
+    timing.timingFunction = StepsTimingFunction::create(4, StepsTimingFunction::StepAtEnd);
     EXPECT_EQ(10, calculateTransformedTime(0, 20, 12, timing));
     EXPECT_EQ(10, calculateTransformedTime(1, 20, 12, timing));
 
     // PlaybackDirectionReverse
     timing.timingFunction = Timing::defaults().timingFunction;
     timing.direction = Timing::PlaybackDirectionReverse;
     EXPECT_EQ(8, calculateTransformedTime(0, 20, 12, timing));
     EXPECT_EQ(8, calculateTransformedTime(1, 20, 12, timing));
 
     // PlaybackDirectionReverse with timing function
-    timing.timingFunction = StepsTimingFunction::create(4, false /* stepAtStart */);
+    timing.timingFunction = StepsTimingFunction::create(4, StepsTimingFunction::StepAtEnd);
     EXPECT_EQ(5, calculateTransformedTime(0, 20, 12, timing));
     EXPECT_EQ(5, calculateTransformedTime(1, 20, 12, timing));
 
     // Timing function when directed time is null.
     EXPECT_TRUE(isNull(calculateTransformedTime(1, 2, nullValue(), timing)));
 
     // Timing function when iterationDuration is infinity
     timing.direction = Timing::PlaybackDirectionNormal;
     EXPECT_EQ(0, calculateTransformedTime(0, std::numeric_limits<double>::infinity(), 0, timing));
     EXPECT_EQ(1, calculateTransformedTime(0, std::numeric_limits<double>::infinity(), 1, timing));
     timing.direction = Timing::PlaybackDirectionReverse;
     EXPECT_EQ(std::numeric_limits<double>::infinity(), calculateTransformedTime(0, std::numeric_limits<double>::infinity(), 0, timing));
     EXPECT_EQ(std::numeric_limits<double>::infinity(), calculateTransformedTime(0, std::numeric_limits<double>::infinity(), 1, timing));
 }
 
 }