Add KeepAliveStateObserver, add the Restart option

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 "base/macros.h"
 #include "base/memory/singleton.h"
 
 struct KeepAliveOptions;
+class KeepAliveStateObserver;
 
 class KeepAliveRegistry {
  public:
   static KeepAliveRegistry* GetInstance();
 
+  void SetObserver(KeepAliveStateObserver* observer);
+
  private:
   friend struct base::DefaultSingletonTraits<KeepAliveRegistry>;
   // Friend to be able to use Register/Unregister
   friend class ScopedKeepAlive;
 
   KeepAliveRegistry();
   ~KeepAliveRegistry();
 
   // Add/Remove entries. Do not use directly, use ScopedKeepAlive instead.
   void Register(const KeepAliveOptions* options);
   void Unregister(const KeepAliveOptions* options);
 
+  void DumpCurrentState() const;
+  KeepAliveOptions ComputeCurrentState() const;
+  void NotifyOfStateDifferences(const KeepAliveOptions& previous_state) const;
+
+  KeepAliveStateObserver* observer_;
+
   std::multiset<const KeepAliveOptions*> registered_keep_alives_;
+  std::multiset<const KeepAliveOptions*> restart_allowed_keep_alives_;
 
   DISALLOW_COPY_AND_ASSIGN(KeepAliveRegistry);
 };
 
 #endif  // CHROME_BROWSER_LIFETIME_KEEP_ALIVE_REGISTRY_H_