Use ScopedTaskEnvironment instead of MessageLoopForUI in device tests.

device/u2f/u2f_register_unittest.cc

Index: device/u2f/u2f_register_unittest.cc
diff --git a/device/u2f/u2f_register_unittest.cc b/device/u2f/u2f_register_unittest.cc
index 6b183da56e302e3a9645a0f0a54a966360a08a1b..5bb55e461aaf531295a81361cbb61bfcf0f56a11 100644
--- a/device/u2f/u2f_register_unittest.cc
+++ b/device/u2f/u2f_register_unittest.cc
@@ -5,6 +5,7 @@
 #include <list>
 
 #include "base/run_loop.h"
+#include "base/test/scoped_task_environment.h"
 #include "base/test/test_io_thread.h"
 #include "device/base/mock_device_client.h"
 #include "device/hid/mock_hid_service.h"
@@ -17,7 +18,10 @@ namespace device {
 
 class U2fRegisterTest : public testing::Test {
  public:
-  U2fRegisterTest() : io_thread_(base::TestIOThread::kAutoStart) {}
+  U2fRegisterTest()
+      : scoped_task_environment_(
+            base::test::ScopedTaskEnvironment::MainThreadType::UI),
+        io_thread_(base::TestIOThread::kAutoStart) {}
 
   void SetUp() override {
     MockHidService* hid_service = device_client_.hid_service();
@@ -25,7 +29,7 @@ class U2fRegisterTest : public testing::Test {
   }
 
  protected:
-  base::MessageLoopForUI message_loop_;
+  base::test::ScopedTaskEnvironment scoped_task_environment_;
   base::TestIOThread io_thread_;
   device::MockDeviceClient device_client_;
 };