Add fallback behavior if the last used profile cannot initialize

chrome/browser/ui/startup/startup_browser_creator.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_UI_STARTUP_STARTUP_BROWSER_CREATOR_H_
 #define CHROME_BROWSER_UI_STARTUP_STARTUP_BROWSER_CREATOR_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 161 matching lines @@
 
 // Returns true if |profile| has exited uncleanly and has not been launched
 // after the unclean exit.
 bool HasPendingUncleanExit(Profile* profile);
 
 // Returns the path that contains the profile that should be loaded on process
 // startup.
 base::FilePath GetStartupProfilePath(const base::FilePath& user_data_dir,
                                      const base::CommandLine& command_line);
 
+#if !defined(OS_CHROMEOS) && !defined(OS_ANDROID)
+// Returns the profile that should be loaded on process startup. This is either
+// the profile returned by GetStartupProfilePath, or the guest profile if the
+// above profile is locked. The guest profile denotes that we should open the
+// user manager. Returns null if the above profile cannot be opened. In case of
+// user manager, returns null if either the guest profile and the system profile
+// cannot be opened.
+Profile* GetStartupProfile(const base::FilePath& user_data_dir,
+                           const base::CommandLine& command_line);
+
+// Returns the profile that should be loaded as the fallback on process startup.
+// As in GetStartupProfile(), the guest profile denotes the user manager.
+// Possible to return null, which means no profile nor the user manager can be
+// opened. The fallback is used if GetStartupProfile() returns null.

[Peter Kasting, 2016/07/11 02:58:59]

Nit: I think this has all the necessary info now, but it's stated in a
roundabout way.  How about:

Returns the profile that should be loaded on process startup when
GetStartupProfile() returns null.  As with GetStartupProfile(), returning the
guest profile means the caller should open the user manager.  This may return
null if no profile nor the user manager can be opened.

...Though this makes me wonder.  If this is only used when GetStartupProfile()
is null, how can this ever return the guest profile?  Wouldn't
GetStartupProfile() being null imply the user manager can't be opened?

[WC Leung, 2016/07/18 17:56:18]

Done.
The normal flow is like this:
 (1) last active profile / selected profile ->
 (2) user manager if profile does not exist or profile is locked
     (does not exist means it is not in profile attribute storage)

The fallback flow is like this:
 (0) normal flow fails ->
 (1) any of the last opened profile which is not locked ->
 (2) user manager ->
 (3) any profile which is not locked ->
 (4) give up

If (1) is selected in the normal flow, but profile initialization fails, then
GetStartupProfile() returns null. In this case it is possible can have the user
manager (2) selected in the fallback flow.

[Peter Kasting, 2016/07/19 21:56:06]

So, is this a case where profile_manager->GetProfile(profile_path) returns null,
but storage.GetProfileAttributesWithPath(profile_path, &entry) returns true?

[WC Leung, 2016/07/27 18:00:05]

Yes.

+Profile* GetFallbackStartupProfile();
+#endif  // !defined(OS_CHROMEOS) && !defined(OS_ANDROID)
+
 #endif  // CHROME_BROWSER_UI_STARTUP_STARTUP_BROWSER_CREATOR_H_