Use ScopedTaskEnvironment instead of MessageLoopForUI in chrome tests.

chrome/browser/chromeos/policy/user_cloud_policy_store_chromeos_unittest.cc

Index: chrome/browser/chromeos/policy/user_cloud_policy_store_chromeos_unittest.cc
diff --git a/chrome/browser/chromeos/policy/user_cloud_policy_store_chromeos_unittest.cc b/chrome/browser/chromeos/policy/user_cloud_policy_store_chromeos_unittest.cc
index fc15dd1af641f4af407174bf746db20ec19074d1..5e5a15d4e7615307101263d38faf36c4fb5f133d 100644
--- a/chrome/browser/chromeos/policy/user_cloud_policy_store_chromeos_unittest.cc
+++ b/chrome/browser/chromeos/policy/user_cloud_policy_store_chromeos_unittest.cc
@@ -15,9 +15,9 @@
 #include "base/location.h"
 #include "base/macros.h"
 #include "base/memory/ptr_util.h"
-#include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
 #include "base/single_thread_task_runner.h"
+#include "base/test/scoped_task_environment.h"
 #include "base/threading/sequenced_worker_pool.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "chromeos/dbus/mock_cryptohome_client.h"
@@ -58,7 +58,9 @@ ACTION_P2(SendSanitizedUsername, call_status, sanitized_username) {
 
 class UserCloudPolicyStoreChromeOSTest : public testing::Test {
  protected:
-  UserCloudPolicyStoreChromeOSTest() {}
+  UserCloudPolicyStoreChromeOSTest()
+      : scoped_task_environment_(
+            base::test::ScopedTaskEnvironment::MainThreadType::UI) {}
 
   void SetUp() override {
     EXPECT_CALL(cryptohome_client_, GetSanitizedUsername(cryptohome_id_, _))
@@ -207,7 +209,7 @@ class UserCloudPolicyStoreChromeOSTest : public testing::Test {
                             .AppendASCII("policy.pub");
   }
 
-  base::MessageLoopForUI loop_;
+  base::test::ScopedTaskEnvironment scoped_task_environment_;
   chromeos::MockCryptohomeClient cryptohome_client_;
   chromeos::MockSessionManagerClient session_manager_client_;
   UserPolicyBuilder policy_;