Revert of Revert of Mojo: Convert scoped_ptr<...>() to nullptr in mojo/embedder.

mojo/embedder/simple_platform_shared_buffer.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 "mojo/embedder/simple_platform_shared_buffer.h"
 
 #include "base/logging.h"
 #include "mojo/embedder/platform_handle_utils.h"
 
 namespace mojo {
@@ skipping 34 matching lines @@
 }
 
 size_t SimplePlatformSharedBuffer::GetNumBytes() const {
   return num_bytes_;
 }
 
 scoped_ptr<PlatformSharedBufferMapping> SimplePlatformSharedBuffer::Map(
     size_t offset,
     size_t length) {
   if (!IsValidMap(offset, length))
-    return scoped_ptr<PlatformSharedBufferMapping>();
+    return nullptr;
 
   return MapNoCheck(offset, length);
 }
 
 bool SimplePlatformSharedBuffer::IsValidMap(size_t offset, size_t length) {
   if (offset > num_bytes_ || length == 0)
     return false;
 
   // Note: This is an overflow-safe check of |offset + length > num_bytes_|
   // (that |num_bytes >= offset| is verified above).
@@ skipping 33 matching lines @@
 void* SimplePlatformSharedBufferMapping::GetBase() const {
   return base_;
 }
 
 size_t SimplePlatformSharedBufferMapping::GetLength() const {
   return length_;
 }
 
 }  // namespace embedder
 }  // namespace mojo