[components/policy] Use ThreadTaskRunnerHandle instead of LoopProxy

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 b6d3d82591f6be0003aa1c0da5bd214b99920c35..db015fd0ce75b3c52a6febb2e5b84b73e7a534a5 100644
--- a/components/policy/core/common/cloud/cloud_policy_validator.cc
+++ b/components/policy/core/common/cloud/cloud_policy_validator.cc
@@ -8,6 +8,7 @@
 #include "base/message_loop/message_loop.h"
 #include "base/metrics/histogram.h"
 #include "base/sequenced_task_runner.h"
+#include "base/single_thread_task_runner.h"
 #include "base/stl_util.h"
 #include "components/policy/core/common/cloud/cloud_policy_constants.h"
 #include "crypto/signature_verifier.h"
@@ -191,13 +192,13 @@ void CloudPolicyValidatorBase::PostValidationTask(
 // static
 void CloudPolicyValidatorBase::PerformValidation(
     scoped_ptr<CloudPolicyValidatorBase> self,
-    scoped_refptr<base::MessageLoopProxy> message_loop,
+    scoped_refptr<base::SingleThreadTaskRunner> task_runner,
     const base::Closure& completion_callback) {
   // Run the validation activities on this thread.
   self->RunValidation();
 
-  // Report completion on |message_loop|.
-  message_loop->PostTask(
+  // Report completion on |task_runner|.
+  task_runner->PostTask(
       FROM_HERE,
       base::Bind(&CloudPolicyValidatorBase::ReportCompletion,
                  base::Passed(&self),