Use initializer_list in ChromePermissionMessageRule ctors

chrome/common/extensions/permissions/chrome_permission_message_rules.h

Index: chrome/common/extensions/permissions/chrome_permission_message_rules.h
diff --git a/chrome/common/extensions/permissions/chrome_permission_message_rules.h b/chrome/common/extensions/permissions/chrome_permission_message_rules.h
index 0256c07b351b5a252d97264828a16b8a8c5dd370..3f75e04b5f6bb86557243b721bd8ca72a763910a 100644
--- a/chrome/common/extensions/permissions/chrome_permission_message_rules.h
+++ b/chrome/common/extensions/permissions/chrome_permission_message_rules.h
@@ -5,6 +5,7 @@
 #ifndef CHROME_COMMON_EXTENSIONS_PERMISSIONS_CHROME_PERMISSION_MESSAGE_RULES_H_
 #define CHROME_COMMON_EXTENSIONS_PERMISSIONS_CHROME_PERMISSION_MESSAGE_RULES_H_
 
+#include <initializer_list>
 #include <set>
 #include <vector>
 
@@ -69,17 +70,17 @@ class ChromePermissionMessageRule {
       const PermissionIDSet& permissions) const;
 
  private:
-  class PermissionIDSetInitializer;
-
   // Create a rule using the default formatter (display the message with ID
   // |message_id|).
-  ChromePermissionMessageRule(int message_id,
-                              const PermissionIDSetInitializer& required,
-                              const PermissionIDSetInitializer& optional);
+  ChromePermissionMessageRule(
+      int message_id,
+      const std::initializer_list<APIPermission::ID>& required,
+      const std::initializer_list<APIPermission::ID>& optional);
   // Create a rule with a custom formatter. Takes ownership of |formatter|.
-  ChromePermissionMessageRule(ChromePermissionMessageFormatter* formatter,
-                              const PermissionIDSetInitializer& required,
-                              const PermissionIDSetInitializer& optional);
+  ChromePermissionMessageRule(
+      ChromePermissionMessageFormatter* formatter,
+      const std::initializer_list<APIPermission::ID>& required,
+      const std::initializer_list<APIPermission::ID>& optional);

[Marc Treib, 2016/11/30 14:42:52]

I'm not very familiar with initializer_lists yet - could all those just say
std::set<APIPermission::ID>& (effectively converting from initializer_list to
set one step earlier), to get rid of the somewhat ugly initializer_list type in
the signature?
Not a big deal though, especially since this is all private.

[tbarzic, 2016/11/30 18:35:44]

I was hoping to use std::set, too, but clang complains when {} is passed to the
constructor with error: "chosen constructor is explicit in copy-initialization"
(http://cplusplus.github.io/LWG/lwg-defects.html#2193 seems relevant).
I guess it could be worked around by passing std:set<>() instead of {}, but this
seems cleaner :)

 
   std::set<APIPermission::ID> required_permissions_;
   std::set<APIPermission::ID> optional_permissions_;