Give PlatformNotificationAction's scalar type field a default value

content/public/common/platform_notification_data.h

Index: content/public/common/platform_notification_data.h
diff --git a/content/public/common/platform_notification_data.h b/content/public/common/platform_notification_data.h
index a2108d0b4b9084b67097d6a707cfa7775fe47b69..74049011c9b26086e76a2b40d8cc7accabab363e 100644
--- a/content/public/common/platform_notification_data.h
+++ b/content/public/common/platform_notification_data.h
@@ -31,7 +31,8 @@ struct CONTENT_EXPORT PlatformNotificationAction {
   ~PlatformNotificationAction();
 
   // Type of the action (button or text input).
-  PlatformNotificationActionType type;
+  PlatformNotificationActionType type =
+      PLATFORM_NOTIFICATION_ACTION_TYPE_BUTTON;
 
   // Action name that the author can use to distinguish them.
   std::string action;