Import //fetch from Web Platform Tests.

third_party/WebKit/LayoutTests/external/wpt/fetch/api/policies/referrer-origin.js

+if (this.document === undefined) {
+  importScripts("/resources/testharness.js");
+  importScripts("../resources/utils.js");
+
+  // A nested importScripts() with a referrer-policy should have no effect
+  // on overall worker policy.
+  importScripts("nested-policy.js");
+}
+
+var referrerOrigin = (new URL("/", location.href)).href;
+var fetchedUrl = RESOURCES_DIR + "inspect-headers.py?headers=referer";
+
+promise_test(function(test) {
+  return fetch(fetchedUrl).then(function(resp) {
+    assert_equals(resp.status, 200, "HTTP status is 200");
+    assert_equals(resp.type , "basic", "Response's type is basic");
+    assert_equals(resp.headers.get("x-request-referer"), referrerOrigin, "request's referrer is " + referrerOrigin);
+  });
+}, "Request's referrer is origin");
+
+promise_test(function(test) {
+  var referrerUrl = "https://{{domains[www]}}:{{ports[https][0]}}/";
+  return fetch(fetchedUrl, { "referrer": referrerUrl }).then(function(resp) {
+    assert_equals(resp.status, 200, "HTTP status is 200");
+    assert_equals(resp.type , "basic", "Response's type is basic");
+    assert_equals(resp.headers.get("x-request-referer"), referrerOrigin, "request's referrer is " + referrerOrigin);
+  });
+}, "Cross-origin referrer is overridden by client origin");
+
+done();