"window.openDatabase is not a function" error in chrome app

When i run my index.html from chrome browser everything works fine but after i created a chrome app from the same files and tried to run the app i get "window.openDatabase is not a function" error.Did i miss something? I've heard that WEBsql is being depreciated but if that's the problem then why is it working on my browser?The only change i made to the folder with my html/js/css files in order to create the chrome app was adding a manifest and a background.js,i also changed window.localstorage with chrome.storage.local