Chrome Extension: Local Storage, how to export

I have a chrome extension that saves a bunch of data to chrome.storage.local. I'm trying to find easy ways to export this data and package it into a file. I'm not constrained on what type of file it is (JSON, CSV, whatever), I just need to be able to export the contents into a standalone (and send-able) file. The extension is only run locally and the user would have access to all local files.

First, you need to get all data.
Then serialize the result.
Finally, offer it as a download to the user.

chrome.storage.local.get(null, function(items) { // null implies all items
    // Convert object to a string.
    var result = JSON.stringify(items);

    // Save as file
    var url = 'data:application/json;base64,' + btoa(result);
    chrome.downloads.download({
        url: url,
        filename: 'filename_of_exported_file.json'
    });
});

To use the chrome.downloads.download method, you need to declare the "downloads" permission in addition to the storage permission in the manifest file.