Revamp the MigrateBrowserPrefs and MigrateUserPrefs code.

chrome/browser/prefs/browser_prefs.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_PREFS_BROWSER_PREFS_H_
 #define CHROME_BROWSER_PREFS_BROWSER_PREFS_H_
 
 class PrefRegistrySimple;
 class PrefService;
 class Profile;
@@ skipping 13 matching lines @@
 // Profile.
 void RegisterUserProfilePrefs(user_prefs::PrefRegistrySyncable* registry);
 
 #if defined(OS_CHROMEOS)
 // Register all prefs that will be used via a PrefService attached to the login
 // Profile.
 void RegisterLoginProfilePrefs(user_prefs::PrefRegistrySyncable* registry);
 #endif
 
 // Migrates prefs from |local_state| to |profile|'s pref store.
+// This should always be executed, and will only migrate the newest changes.

[gab, 2015/02/20 20:33:57]

Change this entire comment to something like:

// Migrate/cleanup deprecated prefs in |local_state|. Over-time, long deprecated
prefs should be removed as new ones are added, but this call should never go
away (even if it becomes an empty call for some time) as it should remain *the*
place to drop deprecated browser prefs at.

[rkaplow, 2015/02/20 21:58:08]

Done. Your suggestion SGTM

 void MigrateBrowserPrefs(Profile* profile, PrefService* local_state);

[gab, 2015/02/20 20:33:57]

Remove |profile| parameter.

[rkaplow, 2015/02/20 21:58:08]

Done.

 
 // Migrates prefs in |profile|'s pref store.
+// This should always be executed, and will only migrate the newest changes.

[gab, 2015/02/20 20:33:57]

Change this entire comment to something like:

// Migrate/cleanup deprecated prefs in |profile_prefs|. Over-time, long
deprecated prefs should be removed as new ones are added, but this call should
never go away (even if it becomes an empty call for some time) as it should
remain *the* place to drop deprecated profile prefs at.

[rkaplow, 2015/02/20 21:58:08]

Done.

 void MigrateUserPrefs(Profile* profile);

[gab, 2015/02/20 20:33:57]

Change the argument from a |Profile* profile| to a |PrefService* profile_prefs|
-- the caller (a Profile) already has the prefs object as a member it can hand
over directly.

[rkaplow, 2015/02/20 21:58:08]

Done.

 
 // Migrates zoom level prefs in |profile|'s pref store to a per-StoragePartition
 // set of prefs.
 void MigrateProfileZoomLevelPrefs(Profile* profile);
 
 }  // namespace chrome
 
 #endif  // CHROME_BROWSER_PREFS_BROWSER_PREFS_H_