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 f0206fdda540184ab00632f2b486af94c6c5912e..8a7ace9748852b17a900df098795fad177674475 100644
--- a/net/http/http_network_session.h
+++ b/net/http/http_network_session.h
@@ -8,6 +8,7 @@
 #include <stddef.h>
 #include <stdint.h>
 
+#include <memory>
 #include <set>
 #include <string>
 #include <unordered_set>
@@ -45,6 +46,7 @@ class HttpProxyClientSocketPool;
 class HttpResponseBodyDrainer;
 class HttpServerProperties;
 class NetLog;
+class NetworkStreamThrottler;
 class ProxyDelegate;
 class ProxyService;
 class QuicClock;
@@ -233,6 +235,9 @@ class NET_EXPORT HttpNetworkSession
   HttpStreamFactory* http_stream_factory_for_websocket() {
     return http_stream_factory_for_websocket_.get();
   }
+  NetworkStreamThrottler* throttler() {
+    return network_stream_throttler_.get();
+  }
   NetLog* net_log() {
     return net_log_;
   }
@@ -290,6 +295,7 @@ 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_;
+  std::unique_ptr<NetworkStreamThrottler> network_stream_throttler_;
 
   NextProtoVector next_protos_;
   bool enabled_protocols_[NUM_VALID_ALTERNATE_PROTOCOLS];