Make an empty content browser test work.

content/browser/browser_main.cc

 // Copyright (c) 2011 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 "content/browser/browser_main.h"
 
 #include "base/allocator/allocator_shim.h"
 #include "base/command_line.h"
 #include "base/debug/trace_event.h"
 #include "base/logging.h"
@@ skipping 322 matching lines @@
 void BrowserMainParts::PreMainMessageLoopStart() {
 }
 
 void BrowserMainParts::PostMainMessageLoopStart() {
 }
 
 void BrowserMainParts::PreMainMessageLoopRun() {
 }
 
 void BrowserMainParts::MainMessageLoopRun() {
+  if (parameters().ui_task)
+    MessageLoopForUI::current()->PostTask(FROM_HERE, parameters().ui_task);
+
 #if defined(OS_MACOSX)
   MessageLoopForUI::current()->Run();
 #else
   MessageLoopForUI::current()->Run(NULL);
 #endif
 }
 
 void BrowserMainParts::PostMainMessageLoopRun() {
 }
 
@@ skipping 63 matching lines @@
   base::win::ScopedCOMInitializer com_initializer;
 #endif  // OS_WIN
 
   base::StatisticsRecorder statistics;
 
   parts->RunMainMessageLoopParts();
 
   TRACE_EVENT_END_ETW("BrowserMain", 0, 0);
   return parts->result_code();
 }