Import //fetch from Web Platform Tests.

third_party/WebKit/LayoutTests/external/wpt/fetch/api/cors/cors-multiple-origins.js

+if (this.document === undefined) {
+  importScripts("/resources/testharness.js");
+  importScripts("../resources/utils.js");
+}
+
+function corsMultipleOrigins(desc, originList, shouldPass) {
+  var urlParameters = "?origin=" + encodeURIComponent(originList.join(", "));
+  var url = "http://{{host}}:{{ports[http][1]}}" + dirname(location.pathname) + RESOURCES_DIR + "preflight.py";
+
+  if (shouldPass) {
+    promise_test(function(test) {
+      return fetch(url + urlParameters).then(function(resp) {
+        assert_equals(resp.status, 200, "Response's status is 200");
+      });
+    }, desc);
+  } else {
+    promise_test(function(test) {
+      return promise_rejects(test, new TypeError(), fetch(url + urlParameters));
+    }, desc);
+  }
+}
+/* Actual origin */
+var origin = "http://{{host}}:{{ports[http][0]}}";
+
+corsMultipleOrigins("3 origins allowed, match the 3rd (" + origin + ")", ["\"\"", "http://example.com", origin], true);
+corsMultipleOrigins("3 origins allowed, match the 3rd (\"*\")", ["\"\"", "http://example.com", "*"], true);
+corsMultipleOrigins("3 origins allowed, match twice (" + origin + ")", ["\"\"", origin, origin], true);
+corsMultipleOrigins("3 origins allowed, match twice (\"*\")", ["*", "http://example.com", "*"], true);
+corsMultipleOrigins("3 origins allowed, match twice (\"*\" and " + origin + ")", ["*", "http://example.com", origin], true);
+corsMultipleOrigins("3 origins allowed, no match", ["", "http://example.com", "https://example2.com"], false);
+
+done();