cleanup: pass string as const reference from c/b/extension

BUG=367418

Review URL: https://codereview.chromium.org/257803002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@267343 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/chrome/browser/extensions/extension_service.h b/chrome/browser/extensions/extension_service.h
index 20e50af..03f18a1 100644
--- a/chrome/browser/extensions/extension_service.h
+++ b/chrome/browser/extensions/extension_service.h
@@ -206,7 +206,7 @@
   //
   // TODO(aa): Remove |external_uninstall| -- this information should be passed
   // to ExtensionPrefs some other way.
-  virtual bool UninstallExtension(std::string extension_id,
+  virtual bool UninstallExtension(const std::string& extension_id,
                                   bool external_uninstall,
                                   base::string16* error);