😴 Skip some KeepAlive registrations on shutdown.

chrome/browser/lifetime/scoped_keep_alive.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_SCOPED_KEEP_ALIVE_H_
 #define CHROME_BROWSER_LIFETIME_SCOPED_KEEP_ALIVE_H_
 
 #include "base/macros.h"
 
 enum class KeepAliveOrigin;
 enum class KeepAliveRestartOption;
 
 // Registers with KeepAliveRegistry on creation and unregisters them
 // on destruction. Use these objects with a scoped_ptr for easy management.
+// Note: The registration will hit a CHECK if it happens while we are
+// shutting down. Caller code should make sure that this can't happen.
 class ScopedKeepAlive {
  public:
   ScopedKeepAlive(KeepAliveOrigin origin, KeepAliveRestartOption restart);
   ~ScopedKeepAlive();
 
  private:
   const KeepAliveOrigin origin_;
   const KeepAliveRestartOption restart_;
 
   DISALLOW_COPY_AND_ASSIGN(ScopedKeepAlive);
 };
 
 #endif  // CHROME_BROWSER_LIFETIME_SCOPED_KEEP_ALIVE_H_