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

cc/surfaces/surface_aggregator.cc

 // Copyright 2014 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/surfaces/surface_aggregator.h"
 
 #include "base/bind.h"
 #include "base/containers/hash_tables.h"
 #include "base/debug/trace_event.h"
 #include "base/logging.h"
@@ skipping 337 matching lines @@
     dest_pass_list_->push_back(copy_pass.Pass());
   }
 }
 
 scoped_ptr<CompositorFrame> SurfaceAggregator::Aggregate(SurfaceId surface_id) {
   Surface* surface = manager_->GetSurfaceForId(surface_id);
   DCHECK(surface);
   contained_surfaces_[surface_id] = surface->frame_index();
   const CompositorFrame* root_surface_frame = surface->GetEligibleFrame();
   if (!root_surface_frame)
-    return scoped_ptr<CompositorFrame>();
+    return nullptr;
   TRACE_EVENT0("cc", "SurfaceAggregator::Aggregate");
 
   scoped_ptr<CompositorFrame> frame(new CompositorFrame);
   frame->delegated_frame_data = make_scoped_ptr(new DelegatedFrameData);
 
   DCHECK(root_surface_frame->delegated_frame_data);
 
   RenderPassList source_pass_list;
 
   SurfaceSet::iterator it = referenced_surfaces_.insert(surface_id).first;
@@ skipping 24 matching lines @@
       surface->TakeLatencyInfo(&frame->metadata.latency_info);
   }
 
   // TODO(jamesr): Aggregate all resource references into the returned frame's
   // resource list.
 
   return frame.Pass();
 }
 
 }  // namespace cc