[Identity] Use const ref on ExtensionTokenKey parameter

Review URL: https://codereview.chromium.org/163013002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@251268 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/extensions/api/identity/extension_token_key.cc

@@ -8,7 +8,7 @@ namespace extensions {
 
 ExtensionTokenKey::ExtensionTokenKey(const std::string& extension_id,
                                      const std::string& account_id,
-                                     const std::set<std::string> scopes)
+                                     const std::set<std::string>& scopes)
     : extension_id(extension_id), account_id(account_id), scopes(scopes) {}
 
 ExtensionTokenKey::~ExtensionTokenKey() {}

chrome/browser/extensions/api/identity/extension_token_key.h

@@ -13,7 +13,7 @@ namespace extensions {
 struct ExtensionTokenKey {
   ExtensionTokenKey(const std::string& extension_id,
                     const std::string& account_id,
-                    const std::set<std::string> scopes);
+                    const std::set<std::string>& scopes);
   ~ExtensionTokenKey();
   bool operator<(const ExtensionTokenKey& rhs) const;
   std::string extension_id;