Implement PerformanceNavigation interface

components/script/dom/webidls/Performance.webidl

@@ -49,3 +49,8 @@ partial interface Performance {
 partial interface Performance {
   PerformanceNavigationTiming timing();
 };
+// https://w3c.github.io/navigation-timing/#extensions-to-the-performance-interface
+partial interface Performance {
+  [SameObject, Exposed=Window]
+  readonly attribute PerformanceNavigation navigation;
+};

components/script/dom/webidls/PerformanceNavigation.webidl

@@ -0,0 +1,18 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+/*
+ * The origin of this IDL file is
+ * https://w3c.github.io/navigation-timing/#the-performancenavigation-interface
+ */
+
+[Exposed=Window]
+interface PerformanceNavigation {
+  const unsigned short TYPE_NAVIGATE = 0;
+  const unsigned short TYPE_RELOAD = 1;
+  const unsigned short TYPE_BACK_FORWARD = 2;
+  const unsigned short TYPE_RESERVED = 255;
+  readonly attribute unsigned short type;
+  readonly attribute unsigned short redirectCount;
+  // [Default] object toJSON();
+};