Enable builtin Mojo JS modules in layout tests

third_party/WebKit/LayoutTests/mojo/resources/mojo-helpers.js

+'use strict';
+
+// Runs a promise_test which depends on the Mojo system API modules available to
+// all layout tests. The test implementation function is called with an Object
+// that exposes common Mojo module interfaces.
+function mojo_test(func, name, properties) {
+  promise_test(() => {
+    return new Promise((resolve, reject) => {
+      define('Mojo layout test module: ' + name, [
+        'mojo/public/js/core',
+        'mojo/public/js/router',
+        'content/public/renderer/service_provider',
+      ], (core, router, serviceProvider) => {
+        try {
+          resolve(func({
+            core: core,
+            router: router,
+
+            // |serviceProvider| is a bit of a misnomer. It should probably be
+            // called |serviceRegistry|, so let's call it that here.
+            serviceRegistry: serviceProvider,
+          }));
+        } catch (e) {
+          reject(e);
+        }
+      });
+    });
+  }, name, properties);
+}