Make BrowserMainParts have an empty implementation to make embedding easier.

content/public/browser/browser_main_parts.cc

Index: content/public/browser/browser_main_parts.cc
===================================================================
--- content/public/browser/browser_main_parts.cc	(revision 0)
+++ content/public/browser/browser_main_parts.cc	(revision 0)
@@ -0,0 +1,17 @@
+// 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 "content/public/browser/browser_main_parts.h"
+
+namespace content {
+
+int BrowserMainParts::PreCreateThreads() {
+  return 0;
+}
+
+bool BrowserMainParts::MainMessageLoopRun(int* result_code) {
+  return false;
+}
+
+}  // namespace content