Add ScopedKeepAlive to c/b/lifetime

chrome/browser/lifetime/keep_alive_registry.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 CHROME_BROWSER_LIFETIME_KEEP_ALIVE_REGISTRY_H_
+#define CHROME_BROWSER_LIFETIME_KEEP_ALIVE_REGISTRY_H_
+
+#include <set>
+#include <string>
+
+#include "base/macros.h"
+#include "base/memory/singleton.h"
+
+enum class OptimizationOptions {
+  NONE = 0,
+  RESTART_ALLOWED,
+  OPTIMIZATION_OPTIONS_LAST = RESTART_ALLOWED
+};
+
+class KeepAliveRegistry {

[Bernhard Bauer, 2016/02/19 17:39:28]

You might be able to move this whole class into an anonymous namespace in
scoped_alive.cc. No one else should use this.

[dgn, 2016/02/19 18:04:28]

Can I do that at the end of the migration? I'm not sure what I will run into
while updating other parts of chrome. 
Also I will probably want to for testing.
And registering observers, which is a legit usage.

[Bernhard Bauer, 2016/02/22 18:19:38]

Okay… Could you make the Register/Unregister methods private and friend
ScopedKeepAlive? Or at the very least, add a comment that these shouldn't be
used directly.

[dgn, 2016/02/22 19:07:19]

Done.

+ public:
+  static KeepAliveRegistry* GetInstance();
+
+  void RegisterToken(const std::string& token, OptimizationOptions opt);
+  void UnregisterToken(const std::string& token, OptimizationOptions opt);
+
+ private:
+  friend struct base::DefaultSingletonTraits<KeepAliveRegistry>;
+
+  KeepAliveRegistry();
+  virtual ~KeepAliveRegistry();
+
+  std::multiset<std::string> registered_tokens_;
+  std::multiset<std::string> reset_allowed_tokens_;

[Bernhard Bauer, 2016/02/19 17:39:28]

|restart_allowed_tokens_|?

[dgn, 2016/02/19 18:04:28]

oops forgot to fix that. Done.

+
+  DISALLOW_COPY_AND_ASSIGN(KeepAliveRegistry);
+};
+
+#endif  // CHROME_BROWSER_LIFETIME_KEEP_ALIVE_REGISTRY_H_