Links in platform apps should open in the system default browser.

chrome/browser/extensions/platform_app_browsertest_util.cc

 // Copyright (c) 2012 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.
 
 #include "chrome/browser/extensions/platform_app_browsertest_util.h"
 
 #include "base/command_line.h"
 #include "base/stringprintf.h"
 #include "chrome/browser/extensions/api/tabs/tabs.h"
 #include "chrome/browser/extensions/extension_function_test_utils.h"
 #include "chrome/browser/extensions/shell_window_registry.h"
 #include "chrome/browser/ui/browser.h"
 #include "chrome/browser/ui/extensions/application_launch.h"
 #include "chrome/browser/ui/extensions/shell_window.h"
 #include "chrome/common/chrome_switches.h"
 #include "content/public/browser/notification_service.h"
 #include "content/public/test/test_utils.h"
 
 using content::WebContents;
 
 namespace utils = extension_function_test_utils;
 
 namespace extensions {
 
 void PlatformAppBrowserTest::SetUpCommandLine(CommandLine* command_line) {
   ExtensionBrowserTest::SetUpCommandLine(command_line);
   command_line->AppendSwitch(switches::kEnableExperimentalExtensionApis);
 }
 
+void PlatformAppBrowserTest::SetUpOnMainThread() {
+  mock_external_url_controller_.reset(new MockExternalUrlController());
+  ShellWindow::SetExternalUrlControllerForTesting(
+      mock_external_url_controller_.get());
+}
+
 const Extension* PlatformAppBrowserTest::LoadAndLaunchPlatformApp(
     const char* name) {
   content::WindowedNotificationObserver app_loaded_observer(
       content::NOTIFICATION_LOAD_COMPLETED_MAIN_FRAME,
       content::NotificationService::AllSources());
 
   const Extension* extension = LoadExtension(
       test_data_dir_.AppendASCII("platform_apps").AppendASCII(name));
   EXPECT_TRUE(extension);
 
@@ skipping 101 matching lines @@
 
 void PlatformAppBrowserTest::CloseShellWindow(ShellWindow* window) {
   content::WindowedNotificationObserver destroyed_observer(
       content::NOTIFICATION_WEB_CONTENTS_DESTROYED,
       content::NotificationService::AllSources());
   window->GetBaseWindow()->Close();
   destroyed_observer.Wait();
 }
 
 }  // namespace extensions