Improve memory estimate of SpdySessionPool in net/ MemoryDumpProvider.

net/proxy/proxy_server.cc

Index: net/proxy/proxy_server.cc
diff --git a/net/proxy/proxy_server.cc b/net/proxy/proxy_server.cc
index 76fa0d6224f346fe45f7eacf9c45c255b5252e1d..dc875eb770d06360cb85e593a39816d880a3d4a2 100644
--- a/net/proxy/proxy_server.cc
+++ b/net/proxy/proxy_server.cc
@@ -209,6 +209,10 @@ ProxyServer::Scheme ProxyServer::GetSchemeFromURI(const std::string& scheme) {
   return GetSchemeFromURIInternal(scheme);
 }
 
+size_t ProxyServer::EstimateMemoryUsage() const {
+  return HostPortPair::EstimateMemoryUsage(host_port_pair_);
+}
+
 // static
 ProxyServer ProxyServer::FromSchemeHostAndPort(
     Scheme scheme,