Reopen a Guest browser and not the User Manager if another Guest browser is already open.

chrome/browser/ui/startup/startup_browser_creator.cc

 // 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.
 
 #include "chrome/browser/ui/startup/startup_browser_creator.h"
 
 #include <algorithm>   // For max().
 #include <set>
 
 #include "apps/app_load_service.h"
@@ skipping 615 matching lines @@
   if (last_opened_profiles.empty()) {
     // If the last used profile is locked or was a guest, show the user manager.
     if (switches::IsNewAvatarMenu()) {
       ProfileInfoCache& profile_info =
           g_browser_process->profile_manager()->GetProfileInfoCache();
       size_t profile_index = profile_info.GetIndexOfProfileWithPath(
           last_used_profile->GetPath());
       bool signin_required = profile_index != std::string::npos &&
           profile_info.ProfileIsSigninRequiredAtIndex(profile_index);
 
-      // Guest or locked profiles cannot be re-opened on startup.
-      if (signin_required || last_used_profile->IsGuestSession()) {
+      // Guest or locked profiles cannot be re-opened on startup. The only
+      // exception is if there's already a Guest window open in a separate
+      // process (for example, launching a new browser after clicking on a
+      // downloaded file in Guest mode).
+      size_t guest_browsers = last_used_profile->IsGuestSession() ?
+          chrome::GetTotalBrowserCountForProfile(
+              last_used_profile->GetOffTheRecordProfile()) : -1;

[sky, 2014/10/30 21:17:51]

I suspect the -1 to a size_t is going to cause warnings. You don't really the
size though right, just if it's empty. Can you convert to a boolean here?

[noms (inactive), 2014/10/31 19:52:10]

Done. Also fixed the logic a bit (there needs to be the extra check for the
guest profile or else it gets triggered for regular profiles with no incognito
browsers...)

+      if (signin_required || (guest_browsers == 0)) {
         UserManager::Show(base::FilePath(),
                           profiles::USER_MANAGER_NO_TUTORIAL,
                           profiles::USER_MANAGER_SELECT_PROFILE_NO_ACTION);
         return true;
       }
     }
-    if (!browser_creator->LaunchBrowser(command_line, last_used_profile,
+
+    Profile* profile_to_open = last_used_profile->IsGuestSession() ?
+        last_used_profile->GetOffTheRecordProfile() : last_used_profile;
+
+    if (!browser_creator->LaunchBrowser(command_line, profile_to_open,
                                         cur_dir, is_process_startup,
                                         is_first_run, return_code)) {
       return false;
     }
   } else {
     // Guest profiles should not be reopened on startup. This can happen if
     // the last used profile was a Guest, but other profiles were also open
     // when Chrome was closed. In this case, pick a different open profile
     // to be the active one, since the Guest profile is never added to the list
     // of open profiles.
@@ skipping 91 matching lines @@
   // If we are showing the app list then chrome isn't shown so load the app
   // list's profile rather than chrome's.
   if (command_line.HasSwitch(switches::kShowAppList)) {
     return AppListService::Get(chrome::HOST_DESKTOP_TYPE_NATIVE)->
         GetProfilePath(user_data_dir);
   }
 
   return g_browser_process->profile_manager()->GetLastUsedProfileDir(
       user_data_dir);
 }