Import //fetch from Web Platform Tests.

third_party/WebKit/LayoutTests/external/wpt/fetch/api/redirect/redirect-location.js

+if (this.document === undefined) {
+  importScripts("/resources/testharness.js");
+  importScripts("../resources/utils.js");
+}
+
+function redirectLocation(desc, redirectUrl, redirectLocation, redirectStatus, redirectMode, shouldPass) {
+  var url = redirectUrl;
+  var urlParameters = "?redirect_status=" + redirectStatus;
+  if (redirectLocation)
+    urlParameters += "&location=" + encodeURIComponent(redirectLocation);
+
+  var requestInit = {"redirect": redirectMode};
+
+  promise_test(function(test) {
+    if (redirectMode === "error" || !shouldPass)
+      return promise_rejects(test, new TypeError(), fetch(url + urlParameters, requestInit));
+    if (redirectLocation && redirectMode === "manual")
+      return fetch(url + urlParameters, requestInit).then(function(resp) {
+        assert_equals(resp.status, 0, "Response's status is 0");
+        assert_equals(resp.type, "opaqueredirect", "Response's type is opaqueredirect");
+        assert_equals(resp.statusText, "", "Response's statusText is \"\"");
+        assert_true(resp.headers.entries().next().done, "Headers should be empty");
+      });
+
+    if (redirectMode === "manual" || redirectMode === "follow")
+      return fetch(url + urlParameters, requestInit).then(function(resp) {
+        assert_equals(resp.status, redirectStatus, "Response's status is " + redirectStatus);
+      });
+    assert_unreached(redirectMode + " is not a valid redirect mode");
+  }, desc);
+}
+
+var redirUrl = RESOURCES_DIR + "redirect.py";
+var locationUrl = "top.txt";
+var invalidLocationUrl = "#invalidurl:";
+var dataLocationUrl = "data:,data%20url";
+// FIXME: We may want to mix redirect-mode and cors-mode.
+// FIXME: Add tests for "error" redirect-mode.
+for (var statusCode of [301, 302, 303, 307, 308]) {
+  redirectLocation("Redirect " + statusCode + " in \"follow\" mode without location", redirUrl, undefined, statusCode, "follow", true);
+  redirectLocation("Redirect " + statusCode + " in \"manual\" mode without location", redirUrl, undefined, statusCode, "manual", true);
+
+  redirectLocation("Redirect " + statusCode + " in \"follow\" mode with invalid location", redirUrl, invalidLocationUrl, statusCode, "follow", false);
+  redirectLocation("Redirect " + statusCode + " in \"manual\" mode with invalid location", redirUrl, invalidLocationUrl, statusCode, "manual", true);
+
+  redirectLocation("Redirect " + statusCode + " in \"follow\" mode with data location", redirUrl, dataLocationUrl, statusCode, "follow", false);
+  redirectLocation("Redirect " + statusCode + " in \"manual\" mode with data location", redirUrl, dataLocationUrl, statusCode, "manual", true);
+}
+
+done();