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

Source/platform/animation/TimingFunctionTestHelper.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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 86 matching lines @@
     return lhs.subType() == ctf.subType();
 }
 
 bool operator==(const StepsTimingFunction& lhs, const TimingFunction& rhs)
 {
     if (rhs.type() != TimingFunction::StepsFunction)
         return false;
 
     const StepsTimingFunction& stf = toStepsTimingFunction(rhs);
     if ((lhs.subType() == StepsTimingFunction::Custom) && (stf.subType() == StepsTimingFunction::Custom))
-        return (lhs.numberOfSteps() == stf.numberOfSteps()) && (lhs.stepAtStart() == stf.stepAtStart());
+        return (lhs.numberOfSteps() == stf.numberOfSteps()) && (lhs.stepAtPosition() == stf.stepAtPosition());
 
     return lhs.subType() == stf.subType();
 }
 
 bool operator==(const ChainedTimingFunction& lhs, const TimingFunction& rhs)
 {
     return ChainedTimingFunctionTestHelper::equals(lhs, rhs);
 }
 
 // Like in the PrintTo case, the generic operator== *must* come after the
@@ skipping 23 matching lines @@
     return false;
 }
 
 // No need to define specific operator!= as they can all come via this function.
 bool operator!=(const TimingFunction& lhs, const TimingFunction& rhs)
 {
     return !(lhs == rhs);
 }
 
 } // namespace WebCore