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

Source/core/css/CSSTimingFunctionValue.cpp

 /*
  * Copyright (C) 2007 Apple Computer, 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 28 matching lines @@
         + String::number(m_y2) + ")";
 }
 
 bool CSSCubicBezierTimingFunctionValue::equals(const CSSCubicBezierTimingFunctionValue& other) const
 {
     return m_x1 == other.m_x1 && m_x2 == other.m_x2 && m_y1 == other.m_y1 && m_y2 == other.m_y2;
 }
 
 String CSSStepsTimingFunctionValue::customCSSText() const
 {
-    return "steps(" + String::number(m_steps) + ", " + (m_stepAtStart ? "start" : "end") + ')';
+    String stepAtPositionString;
+    switch (m_stepAtPosition) {
+    case StepsTimingFunction::StepAtStart:
+        stepAtPositionString = "start";
+        break;
+    case StepsTimingFunction::StepAtMiddle:
+        stepAtPositionString = "middle";
+        break;
+    case StepsTimingFunction::StepAtEnd:
+        stepAtPositionString = "end";
+        break;
+    default:
+        ASSERT_NOT_REACHED();
+        stepAtPositionString = "end";
+        break;
+    }
+    return "steps(" + String::number(m_steps) + ", " + stepAtPositionString + ')';
 }
 
 bool CSSStepsTimingFunctionValue::equals(const CSSStepsTimingFunctionValue& other) const
 {
-    return m_steps == other.m_steps && m_stepAtStart == other.m_stepAtStart;
+    return m_steps == other.m_steps && m_stepAtPosition == other.m_stepAtPosition;
 }
 
 } // namespace WebCore