After locking a profile and showing the User Manager, make Guest the active profile

chrome/browser/profiles/profiles_state.h

 // Copyright 2013 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_PROFILES_PROFILES_STATE_H_
 #define CHROME_BROWSER_PROFILES_PROFILES_STATE_H_
 
 #include <vector>
 #include "base/strings/string16.h"
 
@@ skipping 50 matching lines @@
 
 // If the --google-profile-info flag is turned on, starts an update for a new
 // version of the Gaia profile picture.
 void UpdateGaiaProfilePhotoIfNeeded(Profile* profile);
 
 // Returns the sign-in error controller for the given profile.  Some profiles,
 // like guest profiles, may not have a controller so this function may return
 // NULL.
 SigninErrorController* GetSigninErrorController(Profile* profile);
 
+// If the current active profile (given by prefs::kProfileLastUsed) is locked,
+// changes the active profile to the Guest profile and returns it, otherwise
+// returns NULL. This assumes that the Guest profile has been loaded.
+Profile* SetActiveProfileToGuestIfLocked();
+
 }  // namespace profiles
 
 #endif  // CHROME_BROWSER_PROFILES_PROFILES_STATE_H_