Adds a way to determine id of content handler that created app

mojo/runner/about_fetcher_unittest.cc

 // Copyright 2015 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 "base/at_exit.h"
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
 #include "mojo/application/public/cpp/application_connection.h"
@@ skipping 117 matching lines @@
     //   comments in that method); or
     // - the application manager fails to fetch the requested URL.
     service_provider.set_connection_error_handler(
         [&run_loop]() { run_loop.Quit(); });
 
     URLRequestPtr request(URLRequest::New());
     request->url = url;
     application_manager_->ConnectToApplication(
         nullptr, request.Pass(), std::string(), GURL(),
         service_provider_request.Pass(), nullptr, shell::CapabilityFilter(),
-        base::Closure());
+        base::Closure(), shell::EmptyConnectCallback());
 
     run_loop.Run();
   }
 
   // Overridden from testing::Test:
   void SetUp() override {
     application_manager_.reset(new shell::ApplicationManager(&test_delegate_));
     application_manager_->SetLoaderForURL(
         make_scoped_ptr(new TestLoader(&html_content_handler_)),
         GURL("test:html_content_handler"));
@@ skipping 27 matching lines @@
 
 TEST_F(AboutFetcherTest, UnrecognizedURL) {
   ConnectAndWait("about:some_unrecognized_url");
 
   ASSERT_EQ(0u, html_content_handler()->response_number());
 }
 
 }  // namespace
 }  // namespace runner
 }  // namespace mojo