Cleanup: Pass std::string as const reference from content/

content/public/test/content_browser_test_utils.h

 // Copyright (c) 2012 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 CONTENT_PUBLIC_TEST_CONTENT_BROWSER_TEST_UTILS_H_
 #define CONTENT_PUBLIC_TEST_CONTENT_BROWSER_TEST_UTILS_H_
 
 #include "base/callback.h"
 #include "base/memory/ref_counted.h"
 #include "content/public/common/page_type.h"
@@ skipping 32 matching lines @@
 
 // Navigates |window| to |url|, blocking until the navigation finishes.
 // Returns true if the page was loaded successfully and the last committed
 // URL matches |url|.
 // TODO(alexmos): any tests that use this function and expect successful
 // navigations should do EXPECT_TRUE(NavigateToURL()).
 bool NavigateToURL(Shell* window, const GURL& url);
 
 void LoadDataWithBaseURL(Shell* window,
                          const GURL& url,
-                         const std::string data,
+                         const std::string& data,
                          const GURL& base_url);
 
 // Navigates |window| to |url|, blocking until the given number of navigations
 // finishes.
 void NavigateToURLBlockUntilNavigationsComplete(Shell* window,
                                                 const GURL& url,
                                                 int number_of_navigations);
 
 // Navigates |window| to |url|, blocks until the navigation finishes, and
 // checks that the navigation did not commit (e.g., due to a crash or
@@ skipping 27 matching lines @@
   DISALLOW_COPY_AND_ASSIGN(ShellAddedObserver);
 };
 
 #if defined OS_MACOSX
 void SetWindowBounds(gfx::NativeWindow window, const gfx::Rect& bounds);
 #endif
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_TEST_CONTENT_BROWSER_TEST_UTILS_H_