Allow constructing {Interface,Struct}Ptr from nullptr

mojo/public/cpp/bindings/tests/container_test_util.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/public/cpp/bindings/tests/container_test_util.h"
 
 namespace mojo {
 
 size_t CopyableType::num_instances_ = 0;
 size_t MoveOnlyType::num_instances_ = 0;
@@ skipping 14 matching lines @@
 }
 
 CopyableType::~CopyableType() {
   num_instances_--;
 }
 
 MoveOnlyType::MoveOnlyType() : moved_(false), ptr_(this) {
   num_instances_++;
 }
 
-MoveOnlyType::MoveOnlyType(RValue other)
-    : moved_(true), ptr_(other.object->ptr()) {
+MoveOnlyType::MoveOnlyType(MoveOnlyType&& other)
+    : moved_(true), ptr_(other.ptr()) {
   num_instances_++;
 }
 
-MoveOnlyType& MoveOnlyType::operator=(RValue other) {
+MoveOnlyType& MoveOnlyType::operator=(MoveOnlyType&& other) {
   moved_ = true;
-  ptr_ = other.object->ptr();
+  ptr_ = other.ptr();
   return *this;
 }
 
 MoveOnlyType::~MoveOnlyType() {
   num_instances_--;
 }
 
 }  // namespace mojo