mojo: first take on removing mojo_main_{chromium,standalone}.

mojo/public/c/system/main.h

+// 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.
+
+#ifndef MOJO_PUBLIC_C_SYSTEM_MAIN_H_
+#define MOJO_PUBLIC_C_SYSTEM_MAIN_H_
+
+#include "mojo/public/c/system/types.h"
+
+// Implement MojoMain directly as the entry point for an application.
+//
+// MojoResult MojoMain(MojoHandle service_provider_handle) {
+//   ...
+// }
+//
+// TODO(davemoore): Establish this as part of our SDK for third party mojo
+// application writers.
+
+#if defined(__cplusplus)
+extern "C" {
+#endif
+
+#if defined(WIN32)
+__declspec(dllexport) MojoResult
+    __cdecl MojoMain(MojoHandle service_provider_handle);
+#else  // !defined(WIN32)
+__attribute__((visibility("default"))) MojoResult
+    MojoMain(MojoHandle service_provider_handle);
+#endif  // defined(WIN32)
+
+#ifdef __cplusplus
+}  // extern "C"
+#endif
+
+#endif  // MOJO_PUBLIC_C_SYSTEM_MAIN_H_