Change more base::ListValue methods to use std::unique_ptr.

components/user_manager/user_manager_base.cc

Index: components/user_manager/user_manager_base.cc
diff --git a/components/user_manager/user_manager_base.cc b/components/user_manager/user_manager_base.cc
index 444bb3487009ab59264ffc68418a94396306dd2e..8cd5d50b9c150a4d705c8c92d5ce25fb12fdb9e8 100644
--- a/components/user_manager/user_manager_base.cc
+++ b/components/user_manager/user_manager_base.cc
@@ -16,6 +16,7 @@
 #include "base/location.h"
 #include "base/logging.h"
 #include "base/macros.h"
+#include "base/memory/ptr_util.h"
 #include "base/metrics/histogram.h"
 #include "base/strings/string_util.h"
 #include "base/strings/stringprintf.h"
@@ -851,7 +852,8 @@ void UserManagerBase::GuestUserLoggedIn() {
 void UserManagerBase::AddUserRecord(User* user) {
   // Add the user to the front of the user list.
   ListPrefUpdate prefs_users_update(GetLocalState(), kRegularUsers);
-  prefs_users_update->Insert(0, new base::StringValue(user->email()));
+  prefs_users_update->Insert(
+      0, base::MakeUnique<base::StringValue>(user->email()));
   users_.insert(users_.begin(), user);
 }