Rewrite scoped_ptr<T>(NULL) to use the default ctor in cc/.

cc/trees/layer_tree_host_unittest_context.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 "base/basictypes.h"
 #include "cc/base/thread_impl.h"
 #include "cc/layers/content_layer.h"
 #include "cc/layers/heads_up_display_layer.h"
@@ skipping 1558 matching lines @@
 
   // FakeLayerTreeHostClient implementation.
   virtual scoped_ptr<OutputSurface> CreateOutputSurface() OVERRIDE {
     return scoped_ptr<OutputSurface>();
   }
 
   void RunTest(bool threaded,
                bool delegating_renderer,
                bool impl_side_painting) {
     scoped_ptr<base::Thread> impl_thread;
-    scoped_ptr<cc::Thread> impl_ccthread(NULL);
+    scoped_ptr<cc::Thread> impl_ccthread;
     if (threaded) {
       impl_thread.reset(new base::Thread("LayerTreeTest"));
       impl_ccthread = cc::ThreadImpl::CreateForDifferentThread(
           impl_thread->message_loop_proxy());
       ASSERT_TRUE(impl_ccthread);
     }
 
     LayerTreeSettings settings;
     settings.impl_side_painting = impl_side_painting;
     scoped_ptr<LayerTreeHost> layer_tree_host =
         LayerTreeHost::Create(this, settings, impl_ccthread.Pass());
     EXPECT_FALSE(layer_tree_host);
   }
 };
 
 SINGLE_AND_MULTI_THREAD_TEST_F(
     LayerTreeHostTestCannotCreateIfCannotCreateOutputSurface);
 
 }  // namespace
 }  // namespace cc