Mojo: more idiomatic C++ bindings

mojo/public/cpp/bindings/passable.h

-// Copyright 2013 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 MOJO_PUBLIC_CPP_BINDINGS_PASSABLE_H_
-#define MOJO_PUBLIC_CPP_BINDINGS_PASSABLE_H_
-
-#include "mojo/public/cpp/bindings/lib/bindings_internal.h"
-#include "mojo/public/cpp/system/core.h"
-
-namespace mojo {
-
-template <typename HandleType>
-class Passable {
- public:
-  // |ptr| may be null.
-  explicit Passable(HandleType* ptr) : ptr_(ptr) {
-  }
-
-  bool is_valid() const {
-    return ptr_ && ptr_->is_valid();
-  }
-
-  HandleType get() const {
-    return ptr_ ? *ptr_ : HandleType();
-  }
-
-  HandleType release() MOJO_WARN_UNUSED_RESULT {
-    return ptr_ ? internal::FetchAndReset(ptr_) : HandleType();
-  }
-
-  ScopedHandleBase<HandleType> Pass() {
-    return ScopedHandleBase<HandleType>(release());
-  }
-
- protected:
-  Passable();
-  // The default copy-ctor and operator= are OK.
-
-  HandleType* ptr_;
-};
-
-template <typename HandleType>
-inline Passable<HandleType> MakePassable(HandleType* ptr) {
-  return Passable<HandleType>(ptr);
-}
-
-template <typename HandleType>
-class AssignableAndPassable : public Passable<HandleType> {
- public:
-  explicit AssignableAndPassable(HandleType* ptr) : Passable<HandleType>(ptr) {
-    assert(ptr);
-  }
-
-  void operator=(ScopedHandleBase<HandleType> scoper) {
-    reset(scoper.release());
-  }
-
-  void reset(HandleType obj = HandleType()) {
-    ScopedHandleBase<HandleType>(*this->ptr_);
-    this->ptr_->set_value(obj.value());
-  }
-};
-
-template <typename HandleType>
-inline AssignableAndPassable<HandleType> MakeAssignableAndPassable(
-    HandleType* ptr) {
-  return AssignableAndPassable<HandleType>(ptr);
-}
-
-}  // namespace mojo
-
-#endif  // MOJO_PUBLIC_CPP_BINDINGS_PASSABLE_H_