Use ScopedTaskEnvironment instead of MessageLoopForUI in components tests.

components/policy/core/common/cloud/cloud_policy_validator_unittest.cc

Index: components/policy/core/common/cloud/cloud_policy_validator_unittest.cc
diff --git a/components/policy/core/common/cloud/cloud_policy_validator_unittest.cc b/components/policy/core/common/cloud/cloud_policy_validator_unittest.cc
index 1a773e8b7cb7659cc70f06da849a7fae9ea0b4cf..6356d5017434cfaf356947a7dca220f80c08d37c 100644
--- a/components/policy/core/common/cloud/cloud_policy_validator_unittest.cc
+++ b/components/policy/core/common/cloud/cloud_policy_validator_unittest.cc
@@ -13,10 +13,10 @@
 #include "base/bind.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/strings/string_util.h"
+#include "base/test/scoped_task_environment.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "build/build_config.h"
 #include "components/policy/core/common/cloud/cloud_policy_constants.h"
@@ -43,7 +43,9 @@ ACTION_P(CheckStatus, expected_status) {
 class CloudPolicyValidatorTest : public testing::Test {
  public:
   CloudPolicyValidatorTest()
-      : timestamp_(base::Time::FromJavaTime(PolicyBuilder::kFakeTimestamp)),
+      : scoped_task_environment_(
+            base::test::ScopedTaskEnvironment::MainThreadType::UI),
+        timestamp_(base::Time::FromJavaTime(PolicyBuilder::kFakeTimestamp)),
         timestamp_option_(CloudPolicyValidatorBase::TIMESTAMP_VALIDATED),
         dm_token_option_(CloudPolicyValidatorBase::DM_TOKEN_REQUIRED),
         device_id_option_(CloudPolicyValidatorBase::DEVICE_ID_REQUIRED),
@@ -117,7 +119,7 @@ class CloudPolicyValidatorTest : public testing::Test {
               validator->payload()->SerializeAsString());
   }
 
-  base::MessageLoopForUI loop_;
+  base::test::ScopedTaskEnvironment scoped_task_environment_;
   base::Time timestamp_;
   CloudPolicyValidatorBase::ValidateTimestampOption timestamp_option_;
   CloudPolicyValidatorBase::ValidateDMTokenOption dm_token_option_;