Add Go build support for GN.

mojo/go/c_embedder/c_embedder.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 "content/app/mojo/mojo_init.h"
+#include "mojo/go/c_embedder/c_embedder.h"
 
 #include "base/memory/scoped_ptr.h"
 #include "mojo/embedder/embedder.h"
 #include "mojo/embedder/simple_platform_support.h"
 
-namespace content {
+#ifdef __cplusplus
+extern "C" {
+#endif
 
-void InitializeMojo() {
+void InitializeMojoEmbedder() {
   mojo::embedder::Init(scoped_ptr<mojo::embedder::PlatformSupport>(
       new mojo::embedder::SimplePlatformSupport()));
 }
 
-}  // namespace content
+#ifdef __cplusplus
+}  // extern "C"
+#endif