Make CloudPolicyValidator memory management clearer

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

Index: components/policy/core/common/cloud/cloud_policy_validator.cc
diff --git a/components/policy/core/common/cloud/cloud_policy_validator.cc b/components/policy/core/common/cloud/cloud_policy_validator.cc
index ff6008def367ed6d93f4b3eb54724b59d63df632..3ac136b7cd6c4dc3e58038eb409f4adea49672c6 100644
--- a/components/policy/core/common/cloud/cloud_policy_validator.cc
+++ b/components/policy/core/common/cloud/cloud_policy_validator.cc
@@ -185,13 +185,16 @@ CloudPolicyValidatorBase::CloudPolicyValidatorBase(
   DCHECK(!verification_key_.empty());
 }
 
+// static
 void CloudPolicyValidatorBase::PostValidationTask(
+    std::unique_ptr<CloudPolicyValidatorBase> validator,
     const base::Closure& completion_callback) {
-  background_task_runner_->PostTask(
+  const auto task_runner = validator->background_task_runner_;
+  task_runner->PostTask(
       FROM_HERE,
       base::Bind(&CloudPolicyValidatorBase::PerformValidation,
-                 base::Passed(std::unique_ptr<CloudPolicyValidatorBase>(this)),
-                 base::ThreadTaskRunnerHandle::Get(), completion_callback));
+                 base::Passed(&validator), base::ThreadTaskRunnerHandle::Get(),
+                 completion_callback));
 }
 
 // static