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

cc/animation/scroll_offset_animation_curve.cc

Index: cc/animation/scroll_offset_animation_curve.cc
diff --git a/cc/animation/scroll_offset_animation_curve.cc b/cc/animation/scroll_offset_animation_curve.cc
index 5d51621c3f605115493b66911b392a641e492483..8211a950fe2b24382bc4cf0f7b5c276980ed28a0 100644
--- a/cc/animation/scroll_offset_animation_curve.cc
+++ b/cc/animation/scroll_offset_animation_curve.cc
@@ -38,7 +38,8 @@
   const double v2 = velocity * velocity;
   const double x1 = std::sqrt(r2 / (v2 + 1));
   const double y1 = std::sqrt(r2 * v2 / (v2 + 1));
-  return CubicBezierTimingFunction::Create(x1, y1, 0.58, 1);
+  return CubicBezierTimingFunction::Create(x1, y1, 0.58, 1)
+      .PassAs<TimingFunction>();
 }
 
 }  // namespace
@@ -97,7 +98,7 @@
   curve_clone->initial_value_ = initial_value_;
   curve_clone->total_animation_duration_ = total_animation_duration_;
   curve_clone->last_retarget_ = last_retarget_;
-  return curve_clone.Pass();
+  return curve_clone.PassAs<AnimationCurve>();
 }
 
 void ScrollOffsetAnimationCurve::UpdateTarget(