IOThread: Move more stuff into system context's URLRequestContextStore.

net/url_request/url_request_context.h

Index: net/url_request/url_request_context.h
diff --git a/net/url_request/url_request_context.h b/net/url_request/url_request_context.h
index 96025de24f73d4cc9900873081a671e70e47286d..23b5fc9134616b505dd3bfad20c1ccceac664fc3 100644
--- a/net/url_request/url_request_context.h
+++ b/net/url_request/url_request_context.h
@@ -250,7 +250,7 @@ class NET_EXPORT URLRequestContext
     return http_user_agent_settings_;
   }
   void set_http_user_agent_settings(
-      HttpUserAgentSettings* http_user_agent_settings) {
+      const HttpUserAgentSettings* http_user_agent_settings) {
     http_user_agent_settings_ = http_user_agent_settings;
   }
 
@@ -308,7 +308,7 @@ class NET_EXPORT URLRequestContext
   scoped_refptr<SSLConfigService> ssl_config_service_;
   NetworkDelegate* network_delegate_;
   HttpServerProperties* http_server_properties_;
-  HttpUserAgentSettings* http_user_agent_settings_;
+  const HttpUserAgentSettings* http_user_agent_settings_;
   CookieStore* cookie_store_;
   TransportSecurityState* transport_security_state_;
   CTVerifier* cert_transparency_verifier_;