Record shutdown type UMA

chrome/browser/browser_shutdown.h

 // Copyright (c) 2012 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_BROWSER_SHUTDOWN_H_
 #define CHROME_BROWSER_BROWSER_SHUTDOWN_H_
 
 #include "build/build_config.h"
 
 class PrefRegistrySimple;
@@ skipping 15 matching lines @@
 };
 
 enum ShutdownType {
   // an uninitialized value
   NOT_VALID = 0,
   // the last browser window was closed
   WINDOW_CLOSE,
   // user clicked on the Exit menu item
   BROWSER_EXIT,
   // windows is logging off or shutting down
-  END_SESSION
+  END_SESSION,
+  // This value should always be the last element of this enum.
+  SHUTDOWN_TYPE_MAX_VALUE,

[sky, 2016/09/09 15:40:56]

I'm not a fan of this style. It means the enum has a fake value that isn't
legal, yet has to be dealt with in switch statements because it's defined. How
about a constant instead?

constexpr kMaxShutdownValue = static_cast<int>(END_SESSION) + 1;?

[hashimoto, 2016/09/12 05:10:18]

Sounds good.
Done.

 };
 
 void RegisterPrefs(PrefRegistrySimple* registry);
 
 // Called when the browser starts shutting down so that we can measure shutdown
 // time.
 void OnShutdownStarting(ShutdownType type);
 
 // Get the current shutdown type.
 ShutdownType GetShutdownType();
@@ skipping 37 matching lines @@
 bool IsTryingToQuit();
 
 // Starts to collect shutdown traces. On ChromeOS this will start immediately
 // on AttemptUserExit() and all other systems will start once all tabs are
 // closed.
 void StartShutdownTracing();
 
 }  // namespace browser_shutdown
 
 #endif  // CHROME_BROWSER_BROWSER_SHUTDOWN_H_