CC: Stop TimingFunction inheriting from AnimationCurve.

cc/animation/timing_function.cc

Index: cc/animation/timing_function.cc
diff --git a/cc/animation/timing_function.cc b/cc/animation/timing_function.cc
index 71319e121d8c10ad3bf2f0c0a6b9dfd37c7bf165..eca77edbbf9efcd03915f19a73f554518478c120 100644
--- a/cc/animation/timing_function.cc
+++ b/cc/animation/timing_function.cc
@@ -11,10 +11,6 @@ TimingFunction::TimingFunction() {}
 
 TimingFunction::~TimingFunction() {}
 
-double TimingFunction::Duration() const {
-  return 1.0;
-}
-
 scoped_ptr<CubicBezierTimingFunction> CubicBezierTimingFunction::Create(
     double x1, double y1, double x2, double y2) {
   return make_scoped_ptr(new CubicBezierTimingFunction(x1, y1, x2, y2));
@@ -32,9 +28,9 @@ float CubicBezierTimingFunction::GetValue(double x) const {
   return static_cast<float>(bezier_.Solve(x));
 }
 
-scoped_ptr<AnimationCurve> CubicBezierTimingFunction::Clone() const {
-  return make_scoped_ptr(
-      new CubicBezierTimingFunction(*this)).PassAs<AnimationCurve>();
+scoped_ptr<TimingFunction> CubicBezierTimingFunction::Clone() const {
+  return make_scoped_ptr(new CubicBezierTimingFunction(*this))
+      .PassAs<TimingFunction>();
 }
 
 void CubicBezierTimingFunction::Range(float* min, float* max) const {