Revert 148418 - Always use chromium threads for IO in remoting host

remoting/host/url_request_context.cc

Index: remoting/host/url_request_context.cc
===================================================================
--- remoting/host/url_request_context.cc	(revision 148577)
+++ remoting/host/url_request_context.cc	(working copy)
@@ -8,7 +8,6 @@
 #include "net/base/cert_verifier.h"
 #include "net/base/host_resolver.h"
 #include "net/base/ssl_config_service_defaults.h"
-#include "net/base/transport_security_state.h"
 #include "net/http/http_auth_handler_factory.h"
 #include "net/http/http_network_layer.h"
 #include "net/http/http_network_session.h"
@@ -94,7 +93,6 @@
   storage_.set_http_auth_handler_factory(
       net::HttpAuthHandlerFactory::CreateDefault(host_resolver()));
   storage_.set_http_server_properties(new net::HttpServerPropertiesImpl);
-  storage_.set_transport_security_state(new net::TransportSecurityState);
 
   net::HttpNetworkSession::Params session_params;
   session_params.host_resolver = host_resolver();