Revamp the MigrateBrowserPrefs and MigrateUserPrefs code.

chrome/browser/chromeos/login/default_pinned_apps_field_trial.cc

Index: chrome/browser/chromeos/login/default_pinned_apps_field_trial.cc
diff --git a/chrome/browser/chromeos/login/default_pinned_apps_field_trial.cc b/chrome/browser/chromeos/login/default_pinned_apps_field_trial.cc
deleted file mode 100644
index 4b21f533e68c94b85af0fb4848e98a3e707733bf..0000000000000000000000000000000000000000
--- a/chrome/browser/chromeos/login/default_pinned_apps_field_trial.cc
+++ /dev/null
@@ -1,32 +0,0 @@
-// 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.
-
-#include "chrome/browser/chromeos/login/default_pinned_apps_field_trial.h"
-
-#include "base/basictypes.h"
-#include "base/prefs/pref_registry_simple.h"
-#include "base/prefs/pref_service.h"
-
-namespace chromeos {
-namespace default_pinned_apps_field_trial {
-
-namespace {
-
-// Name of a local state pref to store the list of users that participate
-// the experiment.
-const char kExperimentUsers[] = "DefaultPinnedAppsExperimentUsers";
-
-}  // namespace
-
-void RegisterPrefs(PrefRegistrySimple* registry) {
-  registry->RegisterListPref(kExperimentUsers);
-}
-
-void MigratePrefs(PrefService* local_state) {
-  // TODO(xiyuan): Remove everything in M34.
-  local_state->ClearPref(kExperimentUsers);
-}
-
-}  // namespace default_pinned_apps_field_trial
-}  // namespace chromeos