Simplify some mojo_shell code.

mojo/shell/shell_test_main.cc

 // Copyright 2014 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/bind.h"
 #include "base/command_line.h"
 #include "base/logging.h"
 #include "base/test/launcher/unit_test_launcher.h"
 #include "base/test/test_suite.h"
 #include "mojo/shell/child_process.h"
 #include "mojo/shell/switches.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 int main(int argc, char** argv) {
   base::CommandLine::Init(argc, argv);
   const base::CommandLine& command_line =
       *base::CommandLine::ForCurrentProcess();
 
   if (command_line.HasSwitch(switches::kChildProcess)) {
     base::AtExitManager at_exit;
-    scoped_ptr<mojo::shell::ChildProcess> child_process =
-        mojo::shell::ChildProcess::Create(command_line);
-    CHECK(child_process);
-    child_process->Main();
-    return 0;
+
+    return mojo::shell::ChildProcessMain();
   }
 
   base::TestSuite test_suite(argc, argv);
   return base::LaunchUnitTests(
       argc, argv,
       base::Bind(&base::TestSuite::Run, base::Unretained(&test_suite)));
 }