Add the ability to load multiple apps into app_shell.

extensions/browser/guest_view/web_view/web_view_apitest.cc

Index: extensions/browser/guest_view/web_view/web_view_apitest.cc
diff --git a/extensions/browser/guest_view/web_view/web_view_apitest.cc b/extensions/browser/guest_view/web_view/web_view_apitest.cc
index a30b78a8ce9a561d614a84bb4bf3217d5f1cbfb5..574e3349b49a8f376a5ec86be9d1c36a6c254cac 100644
--- a/extensions/browser/guest_view/web_view/web_view_apitest.cc
+++ b/extensions/browser/guest_view/web_view/web_view_apitest.cc
@@ -140,8 +140,9 @@ void WebViewAPITest::LaunchApp(const std::string& app_location) {
 
   embedded_test_server()->ServeFilesFromDirectory(test_data_dir);
 
-  ASSERT_TRUE(extension_system_->LoadApp(test_data_dir));
-  extension_system_->LaunchApp();
+  const Extension* extension = extension_system_->LoadApp(test_data_dir);
+  ASSERT_TRUE(extension);
+  extension_system_->LaunchApp(extension->id());
 
   ExtensionTestMessageListener launch_listener("LAUNCHED", false);
   ASSERT_TRUE(launch_listener.WaitUntilSatisfied());