Use ScopedTaskEnvironment instead of MessageLoop in chrome unit tests.

chrome/browser/local_discovery/local_domain_resolver_unittest.cc

Index: chrome/browser/local_discovery/local_domain_resolver_unittest.cc
diff --git a/chrome/browser/local_discovery/local_domain_resolver_unittest.cc b/chrome/browser/local_discovery/local_domain_resolver_unittest.cc
index 241c3a14c580e6c24f5e19b8629cbcbd6e6fb87b..d29a4e4179237638d90370aaad5f25f46a9b0efe 100644
--- a/chrome/browser/local_discovery/local_domain_resolver_unittest.cc
+++ b/chrome/browser/local_discovery/local_domain_resolver_unittest.cc
@@ -7,6 +7,7 @@
 #include "base/location.h"
 #include "base/run_loop.h"
 #include "base/single_thread_task_runner.h"
+#include "base/test/scoped_task_environment.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "chrome/browser/local_discovery/service_discovery_client_impl.h"
 #include "net/dns/mdns_client_impl.h"
@@ -100,7 +101,7 @@ class LocalDomainResolverTest : public testing::Test {
 
   net::MockMDnsSocketFactory socket_factory_;
   net::MDnsClientImpl mdns_client_;
-  base::MessageLoop message_loop_;
+  base::test::ScopedTaskEnvironment scoped_task_environment_;
 };
 
 TEST_F(LocalDomainResolverTest, ResolveDomainA) {