[HttpNetworkSession] Flush socket pools on low memory notification.

net/http/http_network_session.cc

Index: net/http/http_network_session.cc
diff --git a/net/http/http_network_session.cc b/net/http/http_network_session.cc
index 06651e967542d13ac5d4fbbb8b2516fe49712447..0f4a2519776962cb0312764c8e263fd6c3863e05 100644
--- a/net/http/http_network_session.cc
+++ b/net/http/http_network_session.cc
@@ -240,6 +240,9 @@ HttpNetworkSession::HttpNetworkSession(const Params& params)
 
   http_server_properties_->SetMaxServerConfigsStoredInProperties(
       params.quic_max_server_configs_stored_in_properties);
+
+  memory_pressure_listener_.reset(new base::MemoryPressureListener(base::Bind(
+      &HttpNetworkSession::OnMemoryPressure, base::Unretained(this))));
 }
 
 HttpNetworkSession::~HttpNetworkSession() {
@@ -402,4 +405,16 @@ ClientSocketPoolManager* HttpNetworkSession::GetSocketPoolManager(
   return NULL;
 }
 
+void HttpNetworkSession::OnMemoryPressure(
+    base::MemoryPressureListener::MemoryPressureLevel memory_pressure_level) {
+  switch (memory_pressure_level) {
+    case base::MemoryPressureListener::MEMORY_PRESSURE_LEVEL_NONE:
+      break;
+    case base::MemoryPressureListener::MEMORY_PRESSURE_LEVEL_MODERATE:
+    case base::MemoryPressureListener::MEMORY_PRESSURE_LEVEL_CRITICAL:
+      CloseIdleConnections();
+      break;
+  }
+}
+
 }  // namespace net