Adds end-to-end tests for VrShell navigation transitions.

chrome/test/data/android/webvr_instrumentation/resources/navigation_e2e.js

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+function setFullscreen(checkbox) {
+  if (checkbox.checked) {
+    document.body.webkitRequestFullScreen();
+  } else {
+    document.webkitCancelFullScreen();
+  }
+}
+function onFullscreenChange() {
+  finishJavaScriptStep();
+}
+document.addEventListener('webkitfullscreenchange', onFullscreenChange, false);
+window.addEventListener('load', finishJavaScriptStep, false);