Enable cookies per default in net. Add an API to disable them by default, and do that in Chrome

chrome/browser/chrome_browser_main.cc

 // 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.
 
 #include "chrome/browser/chrome_browser_main.h"
 
 #include <algorithm>
 #include <string>
 #include <vector>
 
@@ skipping 546 matching lines @@
       profile_(NULL),
       run_message_loop_(true),
       notify_result_(ProcessSingleton::PROCESS_NONE),
       is_first_run_(false),
       first_run_ui_bypass_(false),
       local_state_(NULL),
       restart_last_session_(false) {
   // If we're running tests (ui_task is non-null).
   if (parameters.ui_task)
     browser_defaults::enable_help_app = false;
+
+  // Chrome disallows cookies by default. All code paths that want to use
+  // cookies need to go through one of Chrome's URLRequestContexts which have
+  // a ChromeNetworkDelegate attached that selectively allows cookies again.
+  net::URLRequest::SetDefaultCookiePolicyToBlock();
 }
 
 ChromeBrowserMainParts::~ChromeBrowserMainParts() {
   for (int i = static_cast<int>(chrome_extra_parts_.size())-1; i >= 0; --i)
     delete chrome_extra_parts_[i];
   chrome_extra_parts_.clear();
 }
 
 // This will be called after the command-line has been mutated by about:flags
 void ChromeBrowserMainParts::SetupMetricsAndFieldTrials() {
@@ skipping 1380 matching lines @@
     if (base::win::GetVersion() <= base::win::VERSION_XP)
       uma_name += "_XP";
 
     uma_name += "_PreRead_";
     uma_name += pre_read_percentage;
     AddPreReadHistogramTime(uma_name.c_str(), time);
   }
 #endif
 #endif
 }