Eliminate mojo::Shell client lib class

mojo/shell/public/cpp/message_loop_ref.h

+// Copyright 2016 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_SHELL_PUBLIC_CPP_APPLICATION_RUNNER_REFERENCE_H_
+#define MOJO_SHELL_PUBLIC_CPP_APPLICATION_RUNNER_REFERENCE_H_
+
+#include "base/macros.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/message_loop/message_loop.h"
+#include "mojo/public/cpp/system/core.h"
+
+namespace mojo {
+
+class MessageLoopRefImpl;
+
+// An interface implementation can keep this object as a member variable to
+// hold a reference to the ShellConnection, keeping it alive as long as the
+// bound implementation exists.
+// Since interface implementations can be bound on different threads than the
+// ShellConnection, this class is safe to use on any thread. However, each
+// instance should only be used on one thread at a time (otherwise there'll be
+// races between the AddRef resulting from cloning and destruction).
+class MessageLoopRef {
+ public:
+  virtual ~MessageLoopRef() {}
+
+  virtual scoped_ptr<MessageLoopRef> Clone() = 0;
+};
+
+class MessageLoopRefFactory {
+ public:
+  MessageLoopRefFactory();
+  ~MessageLoopRefFactory();
+
+  void set_quit_closure(const base::Closure& quit_closure) {
+    quit_closure_ = quit_closure;
+  }
+
+  scoped_ptr<MessageLoopRef> CreateRef();
+
+ private:
+  friend MessageLoopRefImpl;
+
+  // Called from MessageLoopRefImpl.
+  void AddRef();
+  void Release();
+
+  base::Closure quit_closure_;
+  int ref_count_ = 0;
+
+  DISALLOW_COPY_AND_ASSIGN(MessageLoopRefFactory);
+};
+
+}  // namespace mojo
+
+#endif  // MOJO_SHELL_PUBLIC_CPP_APPLICATION_RUNNER_REFERENCE_H_