Add KeepAliveStateObserver, add the Restart option

chrome/browser/lifetime/keep_alive_state_observer.h

Index: chrome/browser/lifetime/keep_alive_state_observer.h
diff --git a/chrome/browser/lifetime/keep_alive_state_observer.h b/chrome/browser/lifetime/keep_alive_state_observer.h
new file mode 100644
index 0000000000000000000000000000000000000000..43db402ea9f40d69ba7a1cdc294d93d9c925f3f5
--- /dev/null
+++ b/chrome/browser/lifetime/keep_alive_state_observer.h
@@ -0,0 +1,24 @@
+// 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_STATE_OBSERVER_H_
+#define CHROME_BROWSER_LIFETIME_KEEP_ALIVE_STATE_OBSERVER_H_
+
+#include "base/macros.h"
+
+struct KeepAliveOptions;
+
+class KeepAliveStateObserver {
+ public:
+  virtual void OnRestartAllowed() = 0;

[sky, 2016/02/26 22:13:25]

How about an OnKeepAliveRestartStateChanged(bool can_restart);

[dgn, 2016/03/09 16:35:31]

Yes done. I started with split methods as my current implementations of them
were very different, but that's a detail in the implementation, and should not
be relevant to the interface here.

+  virtual void OnRestartForbidden() = 0;
+
+ protected:
+  KeepAliveStateObserver() {}

[sky, 2016/02/26 22:13:25]

nit: I don't think you need this.

[dgn, 2016/03/09 16:35:31]

Removed.

+  virtual ~KeepAliveStateObserver() {}
+
+  DISALLOW_COPY_AND_ASSIGN(KeepAliveStateObserver);

[sky, 2016/02/26 22:13:25]

you shouldn't need this as KeepAliveStateObserver has pure virtual functions.

[dgn, 2016/03/09 16:35:31]

Done.

+};
+
+#endif  // CHROME_BROWSER_LIFETIME_KEEP_ALIVE_STATE_OBSERVER_H_