Ignore invalid managed user settings values gracefully.

chrome/browser/supervised_user/supervised_user_settings_service.cc

 // Copyright 2014 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/supervised_user/supervised_user_settings_service.h"
 
 #include <stddef.h>
 
 #include <utility>
 
@@ skipping 223 matching lines @@
   Clear();
   int num_added = 0;
   int num_modified = 0;
   std::set<std::string> added_sync_keys;
   for (const SyncData& sync_data : initial_sync_data) {
     DCHECK_EQ(SUPERVISED_USER_SETTINGS, sync_data.GetDataType());
     const ::sync_pb::ManagedUserSettingSpecifics& supervised_user_setting =
         sync_data.GetSpecifics().managed_user_setting();
     std::unique_ptr<base::Value> value =
         JSONReader::Read(supervised_user_setting.value());
+    // null values will cause Chrome to crash when building the settings
+    // dictionary.  Therefore, we ignore them here to prevent such crashes.

[Marc Treib, 2016/08/03 15:30:16]

Just say that SetWithoutPathExpansion below requires non-null values.
Also maybe mention *why* null values can occur here: For wrongly formatted
input.
Finally, nit: Start comment with a capital letter.

+    if (!value) {
+      DLOG(ERROR) << "Invalid managed user setting value: "
+                  << supervised_user_setting.value()
+                  << ". Values must be JSON values.";
+      continue;
+    }
     std::string name_suffix = supervised_user_setting.name();
     std::string name_key = name_suffix;
     base::DictionaryValue* dict = GetDictionaryAndSplitKey(&name_suffix);
     dict->SetWithoutPathExpansion(name_suffix, value.release());
     if (seen_keys.find(name_key) == seen_keys.end()) {
       added_sync_keys.insert(name_key);
       num_added++;
     } else {
       num_modified++;
     }
@@ skipping 227 matching lines @@
   return settings;
 }
 
 void SupervisedUserSettingsService::InformSubscribers() {
   if (!IsReady())
     return;
 
   std::unique_ptr<base::DictionaryValue> settings = GetSettings();
   callback_list_.Notify(settings.get());
 }