Cleanup: Pass std::string as const reference if possible

chrome/browser/devtools/devtools_network_controller_unittest.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <string>
 
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
@@ skipping 50 matching lines @@
     transaction_.reset(new DevToolsNetworkTransaction(
         &controller_, network_transaction.Pass()));
   }
 
   net::HttpRequestInfo* GetRequest() {
     if (!request_)
       request_.reset(new MockHttpRequest(mock_transaction_));
     return request_.get();
   }
 
-  void SetNetworkState(const std::string id, bool offline) {
+  void SetNetworkState(const std::string& id, bool offline) {
     scoped_ptr<DevToolsNetworkConditions> conditions(
         new DevToolsNetworkConditions(offline));
     controller_.SetNetworkState(id, conditions.Pass());
   }
 
   int Start() {
     return transaction_->Start(
         GetRequest(), completion_callback_, net::BoundNetLog());
   }
 
@@ skipping 123 matching lines @@
       "X-DevTools-Emulate-Network-Conditions-Client-Id: 42\r\n"
       "X-DevTools-Request-Initiator: frontend\r\n";
   helper.Start();
 
   EXPECT_FALSE(helper.ShouldFail());
   helper.SetNetworkState(kClientId, true);
   EXPECT_FALSE(helper.ShouldFail());
 }
 
 }  // namespace test