Implementation of network level throttler.

net/http/http_network_session.h

Index: net/http/http_network_session.h
diff --git a/net/http/http_network_session.h b/net/http/http_network_session.h
index 41c5340b0a9124c67b5d17533534a63eced354df..e620f98738b107ba14ae6926092e8c6e94f2802b 100644
--- a/net/http/http_network_session.h
+++ b/net/http/http_network_session.h
@@ -18,6 +18,7 @@
 #include "base/threading/non_thread_safe.h"
 #include "net/base/host_port_pair.h"
 #include "net/base/net_export.h"
+#include "net/base/network_stream_throttler.h"
 #include "net/dns/host_resolver.h"
 #include "net/http/http_auth_cache.h"
 #include "net/http/http_stream_factory.h"
@@ -239,6 +240,7 @@ class NET_EXPORT HttpNetworkSession
   HttpStreamFactory* http_stream_factory_for_websocket() {
     return http_stream_factory_for_websocket_.get();
   }
+  NetworkStreamThrottler* throttler() { return &network_stream_throttler_; }
   NetLog* net_log() {
     return net_log_;
   }
@@ -290,6 +292,7 @@ class NET_EXPORT HttpNetworkSession
   std::unique_ptr<HttpStreamFactory> http_stream_factory_;
   std::unique_ptr<HttpStreamFactory> http_stream_factory_for_websocket_;
   std::set<HttpResponseBodyDrainer*> response_drainers_;
+  NetworkStreamThrottler network_stream_throttler_;
 
   NextProtoVector next_protos_;
   bool enabled_protocols_[NUM_VALID_ALTERNATE_PROTOCOLS];