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

cc/input/top_controls_manager.cc

Index: cc/input/top_controls_manager.cc
diff --git a/cc/input/top_controls_manager.cc b/cc/input/top_controls_manager.cc
index e9722472454784c27d43d098496c9ad763fc2fb5..79353f2b2d15e3f2e1f248560c0492e4d8426e21 100644
--- a/cc/input/top_controls_manager.cc
+++ b/cc/input/top_controls_manager.cc
@@ -180,9 +180,7 @@ gfx::Vector2dF TopControlsManager::Animate(base::TimeTicks monotonic_time) {
 }
 
 void TopControlsManager::ResetAnimations() {
-  if (top_controls_animation_)
-    top_controls_animation_.reset();
-
+  top_controls_animation_ = nullptr;
   animation_direction_ = NO_ANIMATION;
 }