Add Go build support for GN.

mojo/go/c_embedder/c_embedder.cc

Index: mojo/go/c_embedder/c_embedder.cc
diff --git a/content/app/mojo/mojo_init.cc b/mojo/go/c_embedder/c_embedder.cc
similarity index 72%
copy from content/app/mojo/mojo_init.cc
copy to mojo/go/c_embedder/c_embedder.cc
index be427a4ff56e947adf957c0db8bc8e4d0fc22925..00104dce616589d38bc47cb233d8746b69f93cf1 100644
--- a/content/app/mojo/mojo_init.cc
+++ b/mojo/go/c_embedder/c_embedder.cc
@@ -2,17 +2,21 @@
 // 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