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

Index: chrome/browser/chrome_browser_main.cc
diff --git a/chrome/browser/chrome_browser_main.cc b/chrome/browser/chrome_browser_main.cc
index cce078682c0229ab06e2bcdd228ec0f23924427c..2739a08adfa6a82ee6ba49e4e2703f3b0181fae6 100644
--- a/chrome/browser/chrome_browser_main.cc
+++ b/chrome/browser/chrome_browser_main.cc
@@ -564,6 +564,11 @@ ChromeBrowserMainParts::ChromeBrowserMainParts(
   // 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() {