// The actual console is in an iframe from a different origin.
// Fortunately, they share the same TLD, and the iframe sets document.domain,
// so we're able to set ours to the same value. (And we need to.)
document.domain = 'console.aws.amazon.com';

// Grab all checkboxes...
var spans = document.querySelector('iframe').contentDocument.querySelectorAll('tr.list-view-item[type] span.inner');

// ...and click them all:
[].slice.call(spans).forEach(function (span) {
    span.click();
});