Notifier for all users of Gmail™
Please install Offline Notifier for Gmail™ HELPER in order to open GMAIL.com in Chrome™ browser after clicking on Notification in Offline Notifier for Gmail™ (https://chrome.google.com/webstore/detail/offline-email-notifier-fo/clemkkclfcecinlbelmbmmfbclaeifpj)
Chrome APPs have no such API ability yet. What's why that workaround needed. As soon as it will be added, we will update current Chrome application and get rid of extension.