Clarify wording around blocking 3rd party cookies and add lab to block reading of 3rd party cookies

chrome/browser/content_settings/host_content_settings_map.cc

 // Copyright (c) 2010 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/content_settings/host_content_settings_map.h"
 
 #include "base/command_line.h"
 #include "base/string_util.h"
 #include "base/utf_string_conversions.h"
 #include "chrome/browser/browser_thread.h"
@@ skipping 866 matching lines @@
   if (prefs->HasPrefPath(prefs::kCookieBehavior)) {
     int cookie_behavior = prefs->GetInteger(prefs::kCookieBehavior);
     prefs->ClearPref(prefs::kCookieBehavior);
     if (!prefs->HasPrefPath(prefs::kDefaultContentSettings)) {
         SetDefaultContentSetting(CONTENT_SETTINGS_TYPE_COOKIES,
             (cookie_behavior == net::StaticCookiePolicy::BLOCK_ALL_COOKIES) ?
                 CONTENT_SETTING_BLOCK : CONTENT_SETTING_ALLOW);
     }
     if (!prefs->HasPrefPath(prefs::kBlockThirdPartyCookies)) {
       SetBlockThirdPartyCookies(cookie_behavior ==
-          net::StaticCookiePolicy::BLOCK_THIRD_PARTY_COOKIES);
+          net::StaticCookiePolicy::BLOCK_SETTING_THIRD_PARTY_COOKIES);
     }
   }
 }
 
 void HostContentSettingsMap::MigrateObsoletePopupsPref(PrefService* prefs) {
   if (prefs->HasPrefPath(prefs::kPopupWhitelistedHosts)) {
     const ListValue* whitelist_pref =
         prefs->GetList(prefs::kPopupWhitelistedHosts);
     for (ListValue::const_iterator i(whitelist_pref->begin());
          i != whitelist_pref->end(); ++i) {
@@ skipping 70 matching lines @@
   }
 
   for (size_t i = 0; i < move_items.size(); ++i) {
     Value* pattern_settings_dictionary = NULL;
     all_settings_dictionary->RemoveWithoutPathExpansion(
         move_items[i].first, &pattern_settings_dictionary);
     all_settings_dictionary->SetWithoutPathExpansion(
         move_items[i].second, pattern_settings_dictionary);
   }
 }