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

cc/trees/layer_tree_impl.cc

 // Copyright 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/trees/layer_tree_impl.h"
 
 #include <limits>
 #include <set>
 
 #include "base/debug/trace_event.h"
@@ skipping 90 matching lines @@
 
 LayerTreeImpl::~LayerTreeImpl() {
   BreakSwapPromises(SwapPromise::SWAP_FAILS);
 
   // Need to explicitly clear the tree prior to destroying this so that
   // the LayerTreeImpl pointer is still valid in the LayerImpl dtor.
   DCHECK(!root_layer_);
   DCHECK(layers_with_copy_output_request_.empty());
 }
 
-void LayerTreeImpl::Shutdown() {
-  root_layer_ = nullptr;
-}
+void LayerTreeImpl::Shutdown() { root_layer_.reset(); }
 
 void LayerTreeImpl::ReleaseResources() {
   if (root_layer_)
     ReleaseResourcesRecursive(root_layer_.get());
 }
 
 void LayerTreeImpl::SetRootLayer(scoped_ptr<LayerImpl> layer) {
   if (inner_viewport_scroll_layer_)
     inner_viewport_scroll_layer_->SetScrollOffsetDelegate(NULL);
   if (outer_viewport_scroll_layer_)
     outer_viewport_scroll_layer_->SetScrollOffsetDelegate(NULL);
-  inner_viewport_scroll_delegate_proxy_ = nullptr;
-  outer_viewport_scroll_delegate_proxy_ = nullptr;
+  inner_viewport_scroll_delegate_proxy_.reset();
+  outer_viewport_scroll_delegate_proxy_.reset();
 
   root_layer_ = layer.Pass();
   currently_scrolling_layer_ = NULL;
   inner_viewport_scroll_layer_ = NULL;
   outer_viewport_scroll_layer_ = NULL;
   page_scale_layer_ = NULL;
 
   layer_tree_host_impl_->OnCanDrawStateChangedForTree();
 }
 
@@ skipping 39 matching lines @@
 }
 
 scoped_ptr<LayerImpl> LayerTreeImpl::DetachLayerTree() {
   // Clear all data structures that have direct references to the layer tree.
   scrolling_layer_id_from_previous_tree_ =
     currently_scrolling_layer_ ? currently_scrolling_layer_->id() : 0;
   if (inner_viewport_scroll_layer_)
     inner_viewport_scroll_layer_->SetScrollOffsetDelegate(NULL);
   if (outer_viewport_scroll_layer_)
     outer_viewport_scroll_layer_->SetScrollOffsetDelegate(NULL);
-  inner_viewport_scroll_delegate_proxy_ = nullptr;
-  outer_viewport_scroll_delegate_proxy_ = nullptr;
+  inner_viewport_scroll_delegate_proxy_.reset();
+  outer_viewport_scroll_delegate_proxy_.reset();
   inner_viewport_scroll_layer_ = NULL;
   outer_viewport_scroll_layer_ = NULL;
   page_scale_layer_ = NULL;
   currently_scrolling_layer_ = NULL;
 
   render_surface_layer_list_.clear();
   set_needs_update_draw_properties();
   return root_layer_.Pass();
 }
 
@@ skipping 580 matching lines @@
 LayerTreeImpl::CreateScrollbarAnimationController(LayerImpl* scrolling_layer) {
   DCHECK(settings().scrollbar_fade_delay_ms);
   DCHECK(settings().scrollbar_fade_duration_ms);
   base::TimeDelta delay =
       base::TimeDelta::FromMilliseconds(settings().scrollbar_fade_delay_ms);
   base::TimeDelta duration =
       base::TimeDelta::FromMilliseconds(settings().scrollbar_fade_duration_ms);
   switch (settings().scrollbar_animator) {
     case LayerTreeSettings::LinearFade: {
       return ScrollbarAnimationControllerLinearFade::Create(
-          scrolling_layer, layer_tree_host_impl_, delay, duration);
+                 scrolling_layer, layer_tree_host_impl_, delay, duration)
+          .PassAs<ScrollbarAnimationController>();
     }
     case LayerTreeSettings::Thinning: {
       return ScrollbarAnimationControllerThinning::Create(
-          scrolling_layer, layer_tree_host_impl_, delay, duration);
+                 scrolling_layer, layer_tree_host_impl_, delay, duration)
+          .PassAs<ScrollbarAnimationController>();
     }
     case LayerTreeSettings::NoAnimator:
       NOTREACHED();
       break;
   }
-  return nullptr;
+  return scoped_ptr<ScrollbarAnimationController>();
 }
 
 void LayerTreeImpl::DidAnimateScrollOffset() {
   layer_tree_host_impl_->DidAnimateScrollOffset();
 }
 
 bool LayerTreeImpl::use_gpu_rasterization() const {
   return layer_tree_host_impl_->use_gpu_rasterization();
 }
 
@@ skipping 65 matching lines @@
   if (root_layer_scroll_offset_delegate_ == root_layer_scroll_offset_delegate)
     return;
 
   if (!root_layer_scroll_offset_delegate) {
     // Make sure we remove the proxies from their layers before
     // releasing them.
     if (InnerViewportScrollLayer())
       InnerViewportScrollLayer()->SetScrollOffsetDelegate(NULL);
     if (OuterViewportScrollLayer())
       OuterViewportScrollLayer()->SetScrollOffsetDelegate(NULL);
-    inner_viewport_scroll_delegate_proxy_ = nullptr;
-    outer_viewport_scroll_delegate_proxy_ = nullptr;
+    inner_viewport_scroll_delegate_proxy_.reset();
+    outer_viewport_scroll_delegate_proxy_.reset();
   }
 
   root_layer_scroll_offset_delegate_ = root_layer_scroll_offset_delegate;
 
   if (root_layer_scroll_offset_delegate_) {
     root_layer_scroll_offset_delegate_->UpdateRootLayerState(
         TotalScrollOffset(),
         TotalMaxScrollOffset(),
         ScrollableSize(),
         total_page_scale_factor(),
@@ skipping 547 matching lines @@
 
 void LayerTreeImpl::InputScrollAnimationFinished() {
   layer_tree_host_impl_->ScrollEnd();
 }
 
 BlockingTaskRunner* LayerTreeImpl::BlockingMainThreadTaskRunner() const {
   return proxy()->blocking_main_thread_task_runner();
 }
 
 }  // namespace cc