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Test Info:

<!DOCTYPE html>
<title>Ensures content delivered with Content-Type: text/plain header is not prefetched</title>
<!-- Regression test for -->
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="/preload/resources/preload_helper.js"></script>
setup({single_test: true});
window.addEventListener("load", function() {
// This test works by loading a text/plain iframe containing a <script> tag.
// It then injects some post-load JavaScript to serialize the Performance API
// data and pass it back to this document.
var prefetchingIframe = document.getElementById('prefetching-frame');
window.addEventListener("message", function(msg) {
// Parse the Performance API data passed from the plain text iframe.
const entries = JSON.parse(;
const resource_types = [];
for (const entry of entries) {
// If preloading is working correctly, should only see the text document
// represented in the performance information. A 'resource' type indicates
// that we've prefetched something.
let resource_found = false;
for (const t of resource_types) {
if (t == "resource") {
resource_found = true;
assert_false(resource_found, "no resources should be present");
prefetchingIframe.addEventListener('load', function() {
// Pass performance API info back to this document, process in above event handler.
const passMsg = 'parent.postMessage(JSON.stringify(performance.getEntries()));';
// Start the iframe load.
prefetchingIframe.src = "avoid-prefetching-on-text-plain-inner.html";
<iframe id="prefetching-frame"></iframe>