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

cc/base/scoped_ptr_vector.h

 // 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.
 
 #ifndef CC_BASE_SCOPED_PTR_VECTOR_H_
 #define CC_BASE_SCOPED_PTR_VECTOR_H_
 
 #include <algorithm>
 #include <vector>
 
@@ skipping 54 matching lines @@
     DCHECK(!empty());
     return at(size() - 1);
   }
 
   bool empty() const {
     return data_.empty();
   }
 
   scoped_ptr<T> take(iterator position) {
     if (position == end())
-      return scoped_ptr<T>(NULL);
+      return scoped_ptr<T>();
     DCHECK(position < end());
 
     typename std::vector<T*>::iterator writable_position = position;
     scoped_ptr<T> ret(*writable_position);
     *writable_position = NULL;
     return ret.Pass();
   }
 
   scoped_ptr<T> take_back() {
     DCHECK(!empty());
@@ skipping 85 matching lines @@
 
  private:
   std::vector<T*> data_;
 
   DISALLOW_COPY_AND_ASSIGN(ScopedPtrVector);
 };
 
 }  // namespace cc
 
 #endif  // CC_BASE_SCOPED_PTR_VECTOR_H_