Make PermissionManager use ContentSettingsType internally more

components/content_settings/core/common/content_settings_types.h

Index: components/content_settings/core/common/content_settings_types.h
diff --git a/components/content_settings/core/common/content_settings_types.h b/components/content_settings/core/common/content_settings_types.h
index 236cee90a47f2e202bdc561a32bd9bbfff3d23dc..6f6214e189aad10530f5d0c8e364094b6f8673de 100644
--- a/components/content_settings/core/common/content_settings_types.h
+++ b/components/content_settings/core/common/content_settings_types.h
@@ -50,6 +50,10 @@ enum ContentSettingsType {
   CONTENT_SETTINGS_TYPE_PERMISSION_AUTOBLOCKER_DATA,
   CONTENT_SETTINGS_TYPE_SUBRESOURCE_FILTER,
 
+  // This is special-cased in the permissions layer to always allow, and as
+  // such doesn't have associated prefs data.
+  CONTENT_SETTINGS_TYPE_MIDI,
+
   // This is only here temporarily and will be removed when we further unify
   // it with notifications, see crbug.com/563297. No prefs data is stored for
   // this content type, we instead share values with NOTIFICATIONS.