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

chrome/test/chromedriver/chrome/automation_extension.cc

Index: chrome/test/chromedriver/chrome/automation_extension.cc
diff --git a/chrome/test/chromedriver/chrome/automation_extension.cc b/chrome/test/chromedriver/chrome/automation_extension.cc
index 2aa4d22a0ae1d945e50d3f0599ded5fc0e482f68..555f9e9e5dccce2473e0bc5341eca22c24cf01dc 100644
--- a/chrome/test/chromedriver/chrome/automation_extension.cc
+++ b/chrome/test/chromedriver/chrome/automation_extension.cc
@@ -107,7 +107,7 @@ Status AutomationExtension::UpdateWindow(
                                       &result);
 }
 
-Status AutomationExtension::LaunchApp(std::string id) {
+Status AutomationExtension::LaunchApp(const std::string& id) {
   base::ListValue args;
   args.AppendString(id);
   scoped_ptr<base::Value> result;