Simplify animation/transition parsing slightly

Source/core/css/resolver/CSSToStyleMap.cpp

Index: Source/core/css/resolver/CSSToStyleMap.cpp
diff --git a/Source/core/css/resolver/CSSToStyleMap.cpp b/Source/core/css/resolver/CSSToStyleMap.cpp
index 702039253f617321ba85ce1151d4ba807a0f89d7..b81bf83ac7435862a02f812b61fdc56c718ddaaf 100644
--- a/Source/core/css/resolver/CSSToStyleMap.cpp
+++ b/Source/core/css/resolver/CSSToStyleMap.cpp
@@ -396,8 +396,7 @@ PassRefPtr<TimingFunction> CSSToStyleMap::mapAnimationTimingFunction(CSSValue* v
     // FIXME: We should probably only call into this function with a valid
     // single timing function value which isn't initial or inherit. We can
     // currently get into here with initial since the parser expands unset
-    // properties in shorthands to initial and we can get into here with a
-    // value list via the EffectInput/TimingInput code paths.
+    // properties in shorthands to initial.
 
     if (value->isPrimitiveValue()) {
         CSSPrimitiveValue* primitiveValue = toCSSPrimitiveValue(value);
@@ -431,7 +430,7 @@ PassRefPtr<TimingFunction> CSSToStyleMap::mapAnimationTimingFunction(CSSValue* v
         return CubicBezierTimingFunction::create(cubicTimingFunction->x1(), cubicTimingFunction->y1(), cubicTimingFunction->x2(), cubicTimingFunction->y2());
     }
 
-    if (!value->isStepsTimingFunctionValue())
+    if (value->isInitialValue())
         return CSSTimingData::initialTimingFunction();
 
     CSSStepsTimingFunctionValue* stepsTimingFunction = toCSSStepsTimingFunctionValue(value);