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

content/public/test/content_browser_test_utils.cc

Index: content/public/test/content_browser_test_utils.cc
diff --git a/content/public/test/content_browser_test_utils.cc b/content/public/test/content_browser_test_utils.cc
index d20e98e2c7f0322dfd8e0f26de5dde72ab5d6f0f..dab6f7270b64d76440f4654a9f00bc5ce2700a83 100644
--- a/content/public/test/content_browser_test_utils.cc
+++ b/content/public/test/content_browser_test_utils.cc
@@ -53,8 +53,10 @@ void ReloadBlockUntilNavigationsComplete(Shell* window,
   same_tab_observer.Wait();
 }
 
-void LoadDataWithBaseURL(Shell* window, const GURL& url,
-    const std::string data, const GURL& base_url) {
+void LoadDataWithBaseURL(Shell* window,
+                         const GURL& url,
+                         const std::string& data,
+                         const GURL& base_url) {
   WaitForLoadStop(window->web_contents());
   TestNavigationObserver same_tab_observer(window->web_contents(), 1);