Bind a socket to a network if the network handle is set.

webrtc/base/network.cc

Index: webrtc/base/network.cc
diff --git a/webrtc/base/network.cc b/webrtc/base/network.cc
index 488c475137a2ee8d7ddbea1fa2ace59175cc3f36..9f888cca15f65d8f31e5fa3f264dd6c4418dbbf1 100644
--- a/webrtc/base/network.cc
+++ b/webrtc/base/network.cc
@@ -371,6 +371,12 @@ BasicNetworkManager::BasicNetworkManager()
 }
 
 BasicNetworkManager::~BasicNetworkManager() {
+  if (thread_ && network_monitor_ &&
+      thread_->socketserver()->network_binder() == network_monitor_.get()) {
+    // In case that network binder is still being used by the socket server
+    // after it is released here.
+    thread_->socketserver()->set_network_binder(nullptr);
+  }
 }
 
 void BasicNetworkManager::OnNetworksChanged() {
@@ -731,10 +737,13 @@ void BasicNetworkManager::StartNetworkMonitor() {
   if (factory == nullptr) {
     return;
   }
-  network_monitor_.reset(factory->CreateNetworkMonitor());
   if (!network_monitor_) {
-    return;
+    network_monitor_.reset(factory->CreateNetworkMonitor());
+    ASSERT(network_monitor_);

[pthatcher1, 2016/01/15 19:56:11]

Won't some factories return a null monitor?  Isn't that acceptable behavior?  It
was before.

[honghaiz3, 2016/01/15 21:37:36]

Makes sense. Done.

+    ASSERT(thread_ && thread_->socketserver());
+    thread_->socketserver()->set_network_binder(network_monitor_.get());
   }
+
   network_monitor_->SignalNetworksChanged.connect(
       this, &BasicNetworkManager::OnNetworksChanged);
   network_monitor_->Start();
@@ -745,7 +754,6 @@ void BasicNetworkManager::StopNetworkMonitor() {
     return;
   }
   network_monitor_->Stop();
-  network_monitor_.reset();
 }
 
 void BasicNetworkManager::OnMessage(Message* msg) {