A function that is called when save data has finished being retrieved.
@callback saveDataGetFinished
@param {error} err If defined, err is the error that occurred when retrieving the data.
@param {object} data The key-value pairs of data that were previously saved.
 
Retrieve data previously stored with {@link Splat.saveData.set}.
@alias Splat.saveData.get
@param {string | Array} keys A single key or array of key names of data items to retrieve.
@param {saveDataGetFinished} callback A callback that is called with the data when it has been retrieved.
function chromeStorageGet(keys, callback) {
  window.chrome.storage.sync.get(keys, function(data) {
    if (window.chrome.runtime.lastError) {
      callback(window.chrome.runtime.lastError);
    } else {
      callback(undefined, data);
    }
  });
}