Use ScopedTaskEnvironment instead of MessageLoop in chrome unit tests.

chrome/browser/chromeos/net/network_state_notifier_unittest.cc

Index: chrome/browser/chromeos/net/network_state_notifier_unittest.cc
diff --git a/chrome/browser/chromeos/net/network_state_notifier_unittest.cc b/chrome/browser/chromeos/net/network_state_notifier_unittest.cc
index 3b9bfb387afdc4ea08e36398eccf2befbf489e38..c69dfb7316400c700a7b7f6013c13c7180f71ffd 100644
--- a/chrome/browser/chromeos/net/network_state_notifier_unittest.cc
+++ b/chrome/browser/chromeos/net/network_state_notifier_unittest.cc
@@ -8,6 +8,7 @@
 
 #include "base/macros.h"
 #include "base/run_loop.h"
+#include "base/test/scoped_task_environment.h"
 #include "chromeos/dbus/dbus_thread_manager.h"
 #include "chromeos/dbus/shill_device_client.h"
 #include "chromeos/dbus/shill_service_client.h"
@@ -112,7 +113,7 @@ class NetworkStateNotifierTest : public testing::Test {
   }
 
   std::unique_ptr<NetworkConnectTestDelegate> network_connect_delegate_;
-  base::MessageLoop message_loop_;
+  base::test::ScopedTaskEnvironment scoped_task_environment_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(NetworkStateNotifierTest);