Revert of cc: Remove use of PassAs() and constructor-casting with scoped_ptr.

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 2531cc69f36457ccac33f807ad39ce960002f147..97e0d4bc0b13aff704921a5c8cec943723291e76 100644
--- a/cc/animation/timing_function.cc
+++ b/cc/animation/timing_function.cc
@@ -42,25 +42,30 @@
 }
 
 scoped_ptr<TimingFunction> CubicBezierTimingFunction::Clone() const {
-  return make_scoped_ptr(new CubicBezierTimingFunction(*this));
+  return make_scoped_ptr(new CubicBezierTimingFunction(*this))
+      .PassAs<TimingFunction>();
 }
 
 // These numbers come from
 // http://www.w3.org/TR/css3-transitions/#transition-timing-function_tag.
 scoped_ptr<TimingFunction> EaseTimingFunction::Create() {
-  return CubicBezierTimingFunction::Create(0.25, 0.1, 0.25, 1.0);
+  return CubicBezierTimingFunction::Create(
+      0.25, 0.1, 0.25, 1.0).PassAs<TimingFunction>();
 }
 
 scoped_ptr<TimingFunction> EaseInTimingFunction::Create() {
-  return CubicBezierTimingFunction::Create(0.42, 0.0, 1.0, 1.0);
+  return CubicBezierTimingFunction::Create(
+      0.42, 0.0, 1.0, 1.0).PassAs<TimingFunction>();
 }
 
 scoped_ptr<TimingFunction> EaseOutTimingFunction::Create() {
-  return CubicBezierTimingFunction::Create(0.0, 0.0, 0.58, 1.0);
+  return CubicBezierTimingFunction::Create(
+      0.0, 0.0, 0.58, 1.0).PassAs<TimingFunction>();
 }
 
 scoped_ptr<TimingFunction> EaseInOutTimingFunction::Create() {
-  return CubicBezierTimingFunction::Create(0.42, 0.0, 0.58, 1);
+  return CubicBezierTimingFunction::Create(
+      0.42, 0.0, 0.58, 1).PassAs<TimingFunction>();
 }
 
 }  // namespace cc