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

cc/trees/layer_tree_host_perftest.cc

 // Copyright 2012 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_host.h"
 
 #include <sstream>
 
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
@@ skipping 287 matching lines @@
   virtual void CleanUpAndEndTest(LayerTreeHostImpl* host_impl) override {
     clean_up_started_ = true;
     MainThreadTaskRunner()->PostTask(
         FROM_HERE,
         base::Bind(&BrowserCompositorInvalidateLayerTreePerfTest::
                         CleanUpAndEndTestOnMainThread,
                    base::Unretained(this)));
   }
 
   void CleanUpAndEndTestOnMainThread() {
-    tab_contents_->SetTextureMailbox(TextureMailbox(),
-                                     scoped_ptr<SingleReleaseCallback>());
+    tab_contents_->SetTextureMailbox(TextureMailbox(), nullptr);
     EndTest();
   }
 
   virtual bool CleanUpStarted() override { return clean_up_started_; }
 
  private:
   scoped_refptr<TextureLayer> tab_contents_;
   unsigned next_sync_point_;
   bool clean_up_started_;
 };
 
 TEST_F(BrowserCompositorInvalidateLayerTreePerfTest, DenseBrowserUI) {
   measure_commit_cost_ = true;
   SetTestName("dense_layer_tree");
   ReadTestFile("dense_layer_tree");
   RunTestWithImplSidePainting();
 }
 
 // Simulates a page with several large, transformed and animated layers.
 TEST_F(LayerTreeHostPerfTestJsonReader, HeavyPageThreadedImplSide) {
   begin_frame_driven_drawing_ = true;
   measure_commit_cost_ = true;
   SetTestName("heavy_page");
   ReadTestFile("heavy_layer_tree");
   RunTestWithImplSidePainting();
 }
 
 }  // namespace
 }  // namespace cc