Rewrite std::string("") to std::string(), Linux edition.

chrome/browser/policy/cloud/cloud_policy_refresh_scheduler_unittest.cc

Index: chrome/browser/policy/cloud/cloud_policy_refresh_scheduler_unittest.cc
diff --git a/chrome/browser/policy/cloud/cloud_policy_refresh_scheduler_unittest.cc b/chrome/browser/policy/cloud/cloud_policy_refresh_scheduler_unittest.cc
index 269ca756201d9dcb277cd0d185856203971ebcc3..9f3c403225a45523a172ef28f80b67bf9f7c41fc 100644
--- a/chrome/browser/policy/cloud/cloud_policy_refresh_scheduler_unittest.cc
+++ b/chrome/browser/policy/cloud/cloud_policy_refresh_scheduler_unittest.cc
@@ -127,7 +127,7 @@ TEST_F(CloudPolicyRefreshSchedulerTest, InitialRefreshManagedAlreadyFetched) {
 }
 
 TEST_F(CloudPolicyRefreshSchedulerTest, Unregistered) {
-  client_.SetDMToken("");
+  client_.SetDMToken(std::string());
   scoped_ptr<CloudPolicyRefreshScheduler> scheduler(CreateRefreshScheduler());
   client_.NotifyPolicyFetched();
   client_.NotifyRegistrationStateChanged();
@@ -182,7 +182,7 @@ TEST_F(CloudPolicyRefreshSchedulerSteadyStateTest, OnRegistrationStateChanged) {
   EXPECT_EQ(GetLastDelay(), base::TimeDelta());
 
   task_runner_->ClearPendingTasks();
-  client_.SetDMToken("");
+  client_.SetDMToken(std::string());
   client_.NotifyRegistrationStateChanged();
   EXPECT_TRUE(task_runner_->GetPendingTasks().empty());
 }