Fix missing const-reference on function parameter.

This issue was found by a linter.

R=ben@chromium.org

BUG=

Review URL: https://chromiumcodereview.appspot.com/23272005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@220074 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/ui/find_bar/find_bar_host_browsertest.cc

@@ -168,7 +168,7 @@ class FindInPageControllerTest : public InProcessBrowserTest {
     return start_x_position;
   }
 
-  GURL GetURL(const std::string filename) {
+  GURL GetURL(const std::string& filename) {
     return ui_test_utils::GetTestUrl(
         base::FilePath().AppendASCII("find_in_page"),
         base::FilePath().AppendASCII(filename));