Coverity: Pass parameters by reference.

chrome/browser/automation/testing_automation_provider.h

 // Copyright (c) 2011 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.
 
 #ifndef CHROME_BROWSER_AUTOMATION_TESTING_AUTOMATION_PROVIDER_H_
 #define CHROME_BROWSER_AUTOMATION_TESTING_AUTOMATION_PROVIDER_H_
 #pragma once
 
 #include "base/basictypes.h"
 #include "base/scoped_ptr.h"
@@ skipping 348 matching lines @@
   void GetBlockedPopupCount(int handle, int* count);
 
   // Captures the entire page for the given tab and saves it as PNG at the
   // given path.
   void CaptureEntirePageAsPNG(int tab_handle, const FilePath& path,
                               IPC::Message* reply_message);
 
   // Generic pattern for pyautolib
   // Uses the JSON interface for input/output.
   void SendJSONRequest(int handle,
-                       std::string json_request,
+                       const std::string& json_request,
                        IPC::Message* reply_message);
 
   // Method ptr for json handlers.
   // Uses the JSON interface for input/output.
   typedef void (TestingAutomationProvider::*JsonHandler)(DictionaryValue*,
                                                          IPC::Message*);
 
   // Method ptr for json handlers that take a browser argument.
   // Uses the JSON interface for input/output.
   typedef void (TestingAutomationProvider::*BrowserJsonHandler)(
@@ skipping 669 matching lines @@
   // Used to enumerate browser profiles.
   scoped_refptr<ImporterList> importer_list_;
 
   // The stored data for the ImportSettings operation.
   ImportSettingsData import_settings_data_;
 
   DISALLOW_COPY_AND_ASSIGN(TestingAutomationProvider);
 };
 
 #endif  // CHROME_BROWSER_AUTOMATION_TESTING_AUTOMATION_PROVIDER_H_