cc: Change scoped_ptr<T>() to nullptr.

cc/debug/unittest_only_benchmark_impl.cc

 // Copyright 2013 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/debug/unittest_only_benchmark_impl.h"
 
 #include "base/message_loop/message_loop_proxy.h"
 #include "base/values.h"
 
 namespace cc {
 
 UnittestOnlyBenchmarkImpl::UnittestOnlyBenchmarkImpl(
     scoped_refptr<base::MessageLoopProxy> origin_loop,
     base::Value* settings,
     const DoneCallback& callback)
     : MicroBenchmarkImpl(callback, origin_loop) {}
 
 UnittestOnlyBenchmarkImpl::~UnittestOnlyBenchmarkImpl() {}
 
 void UnittestOnlyBenchmarkImpl::DidCompleteCommit(LayerTreeHostImpl* host) {
-  NotifyDone(scoped_ptr<base::Value>());
+  NotifyDone(nullptr);
 }
 
 }  // namespace cc