Signing out forces the lock bit to be removed.

chrome/browser/signin/chrome_signin_client.cc

 // Copyright 2014 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.
 
 #include "chrome/browser/signin/chrome_signin_client.h"
 
 #include "base/command_line.h"
 #include "base/guid.h"
 #include "base/prefs/pref_service.h"
 #include "chrome/browser/browser_process.h"
@@ skipping 150 matching lines @@
   }
   return signin_scoped_device_id;
 }
 
 void ChromeSigninClient::OnSignedOut() {
   GetPrefs()->ClearPref(prefs::kGoogleServicesSigninScopedDeviceId);
   ProfileInfoCache& cache =
       g_browser_process->profile_manager()->GetProfileInfoCache();
   size_t index = cache.GetIndexOfProfileWithPath(profile_->GetPath());
   cache.SetLocalAuthCredentialsOfProfileAtIndex(index, std::string());
+  cache.SetProfileSigninRequiredAtIndex(index, false);

[Roger Tawa OOO till Jul 10th, 2014/10/31 20:43:55]

Should calling SetLocalAuthCredentialsOfProfileAtIndex() with an empty string do
this automatically?

 }
 
 net::URLRequestContextGetter* ChromeSigninClient::GetURLRequestContext() {
   return profile_->GetRequestContext();
 }
 
 bool ChromeSigninClient::ShouldMergeSigninCredentialsIntoCookieJar() {
   // If inline sign in is enabled, but account consistency is not, the user's
   // credentials should be merge into the cookie jar.
   return !switches::IsEnableWebBasedSignin() &&
@@ skipping 67 matching lines @@
   if (!callbacks_.empty())
     return;
   // Note that it's allowed to call this method multiple times without an
   // intervening call to |RegisterForCookieChangedNotification()|.
   content::Source<Profile> source(profile_);
   if (!registrar_.IsRegistered(
       this, chrome::NOTIFICATION_COOKIE_CHANGED, source))
     return;
   registrar_.Remove(this, chrome::NOTIFICATION_COOKIE_CHANGED, source);
 }