Reland: Lazily initialize MessageLoop for faster thread startup

net/android/network_change_notifier_android.cc

Index: net/android/network_change_notifier_android.cc
diff --git a/net/android/network_change_notifier_android.cc b/net/android/network_change_notifier_android.cc
index a6ea628e1f0c0ceb4fcee652b4c335d27763fc6b..982923507d8a1b2321b49771e8390e66ae350f32 100644
--- a/net/android/network_change_notifier_android.cc
+++ b/net/android/network_change_notifier_android.cc
@@ -173,6 +173,9 @@ NetworkChangeNotifierAndroid::NetworkChangeNotifierAndroid(
   delegate_->AddObserver(this);
   dns_config_service_thread_->StartWithOptions(
       base::Thread::Options(base::MessageLoop::TYPE_IO, 0));
+  // Wait until Init is called on the DNS config thread before
+  // calling InitAfterStart.
+  dns_config_service_thread_->WaitUntilThreadStarted();
   dns_config_service_thread_->InitAfterStart();
 }