Enable Image Worker for guest-media-app (untrusted Web UI).

Won't show any changes until http://crrev.com/c/1895263 (serving bundle app resources) lands

Bug: 996088, b/142091425

Change-Id: I5fe3a942ac56f7eff30b0856f9e6ecf57bf28dc8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1895262Reviewed-by: Trent Apted <tapted@chromium.org>
Commit-Queue: David Lei <dlei@google.com>
Cr-Commit-Position: refs/heads/master@{#714902}

chromeos/components/media_app_ui/BUILD.gn

@@ -30,6 +30,7 @@ js2gtest("browser_tests_js") {
   test_type = "mojo_lite_webui"
 
   sources = [
+    "test/media_app_guest_ui_browsertest.js",
     "test/media_app_ui_browsertest.js",
   ]
 

chromeos/components/media_app_ui/media_app_guest_ui.cc

@@ -39,6 +39,9 @@ content::WebUIDataSource* MediaAppGuestUI::CreateDataSource() {
   }
 
   source->DisableDenyXFrameOptions();
+  std::string csp =
+      std::string("worker-src ") + kChromeUIMediaAppGuestURL + ";";
+  source->OverrideContentSecurityPolicyChildSrc(csp);
   return source;
 }
 

chromeos/components/media_app_ui/test/media_app_guest_ui_browsertest.js

+// Copyright 2019 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.
+
+/**
+ * @fileoverview Test suite for chrome://media-app-guest.
+ */
+
+GEN('#include "chromeos/constants/chromeos_features.h"');
+
+var MediaAppGuestUIBrowserTest = class extends testing.Test {
+  /** @override */
+  get browsePreload() {
+    return 'chrome://media-app-guest/app.html';
+  }
+
+  /** @override */
+  get featureList() {
+    return {enabled: ['chromeos::features::kMediaApp']};
+  }
+
+  /** @override */
+  get runAccessibilityChecks() {
+    return false;
+  }
+
+  /** @override */
+  preLoad() {
+    document.addEventListener('DOMContentLoaded', () => {
+      const mojoBindingsLite = document.createElement('script');
+      mojoBindingsLite.src = 'chrome://resources/mojo/mojo/public/js/mojo_bindings_lite.js';
+      document.head.appendChild(mojoBindingsLite);
+    });
+  }
+};
+
+// Test web workers can be spawned from chrome://media-app-guest. Errors
+// will be logged in console from web_ui_browser_test.cc.
+TEST_F('MediaAppGuestUIBrowserTest', 'GuestCanSpawnWorkers', () => {
+  let error = null;
+
+  try {
+    const worker = new Worker('js/app_drop_target_module.js');
+  } catch (e) {
+    error = e;
+  }
+
+  assertEquals(error, null);
+});
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