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

cc/trees/layer_tree_impl.cc

Index: cc/trees/layer_tree_impl.cc
diff --git a/cc/trees/layer_tree_impl.cc b/cc/trees/layer_tree_impl.cc
index 6e44bfc80355276bcc249f751725ed695b6fbf89..ea9c1d012f14c9097bbd0dd3b262de1dfe1696bc 100644
--- a/cc/trees/layer_tree_impl.cc
+++ b/cc/trees/layer_tree_impl.cc
@@ -108,7 +108,9 @@ LayerTreeImpl::~LayerTreeImpl() {
   DCHECK(layers_with_copy_output_request_.empty());
 }
 
-void LayerTreeImpl::Shutdown() { root_layer_.reset(); }
+void LayerTreeImpl::Shutdown() {
+  root_layer_ = nullptr;
+}
 
 void LayerTreeImpl::ReleaseResources() {
   if (root_layer_)
@@ -120,8 +122,8 @@ void LayerTreeImpl::SetRootLayer(scoped_ptr<LayerImpl> layer) {
     inner_viewport_scroll_layer_->SetScrollOffsetDelegate(NULL);
   if (outer_viewport_scroll_layer_)
     outer_viewport_scroll_layer_->SetScrollOffsetDelegate(NULL);
-  inner_viewport_scroll_delegate_proxy_.reset();
-  outer_viewport_scroll_delegate_proxy_.reset();
+  inner_viewport_scroll_delegate_proxy_ = nullptr;
+  outer_viewport_scroll_delegate_proxy_ = nullptr;
 
   root_layer_ = layer.Pass();
   currently_scrolling_layer_ = NULL;
@@ -181,8 +183,8 @@ scoped_ptr<LayerImpl> LayerTreeImpl::DetachLayerTree() {
     inner_viewport_scroll_layer_->SetScrollOffsetDelegate(NULL);
   if (outer_viewport_scroll_layer_)
     outer_viewport_scroll_layer_->SetScrollOffsetDelegate(NULL);
-  inner_viewport_scroll_delegate_proxy_.reset();
-  outer_viewport_scroll_delegate_proxy_.reset();
+  inner_viewport_scroll_delegate_proxy_ = nullptr;
+  outer_viewport_scroll_delegate_proxy_ = nullptr;
   inner_viewport_scroll_layer_ = NULL;
   outer_viewport_scroll_layer_ = NULL;
   page_scale_layer_ = NULL;
@@ -783,19 +785,17 @@ LayerTreeImpl::CreateScrollbarAnimationController(LayerImpl* scrolling_layer) {
   switch (settings().scrollbar_animator) {
     case LayerTreeSettings::LinearFade: {
       return ScrollbarAnimationControllerLinearFade::Create(
-                 scrolling_layer, layer_tree_host_impl_, delay, duration)
-          .PassAs<ScrollbarAnimationController>();
+          scrolling_layer, layer_tree_host_impl_, delay, duration);
     }
     case LayerTreeSettings::Thinning: {
       return ScrollbarAnimationControllerThinning::Create(
-                 scrolling_layer, layer_tree_host_impl_, delay, duration)
-          .PassAs<ScrollbarAnimationController>();
+          scrolling_layer, layer_tree_host_impl_, delay, duration);
     }
     case LayerTreeSettings::NoAnimator:
       NOTREACHED();
       break;
   }
-  return scoped_ptr<ScrollbarAnimationController>();
+  return nullptr;
 }
 
 void LayerTreeImpl::DidAnimateScrollOffset() {
@@ -881,8 +881,8 @@ void LayerTreeImpl::SetRootLayerScrollOffsetDelegate(
       InnerViewportScrollLayer()->SetScrollOffsetDelegate(NULL);
     if (OuterViewportScrollLayer())
       OuterViewportScrollLayer()->SetScrollOffsetDelegate(NULL);
-    inner_viewport_scroll_delegate_proxy_.reset();
-    outer_viewport_scroll_delegate_proxy_.reset();
+    inner_viewport_scroll_delegate_proxy_ = nullptr;
+    outer_viewport_scroll_delegate_proxy_ = nullptr;
   }
 
   root_layer_scroll_offset_delegate_ = root_layer_scroll_offset_delegate;