Use ChannelMojo from the browser to NaCl loader process.

ppapi/nacl_irt/plugin_startup.cc

Index: ppapi/nacl_irt/plugin_startup.cc
diff --git a/ppapi/nacl_irt/plugin_startup.cc b/ppapi/nacl_irt/plugin_startup.cc
index d234a2d8e0c2d952b66ec51f9e33f9eef5ccf6da..2b9270ef302544ba577420cea49dcf61c7ba286c 100644
--- a/ppapi/nacl_irt/plugin_startup.cc
+++ b/ppapi/nacl_irt/plugin_startup.cc
@@ -65,13 +65,17 @@ void SetIPCChannelHandles(
   g_manifest_service_handle = new IPC::ChannelHandle(manifest_service_handle);
 }
 
-void StartUpPlugin() {
+void StartUpPlugin(bool initialize_mojo) {
   // The start up must be called only once.
   DCHECK(!g_shutdown_event);
   DCHECK(!g_io_thread);
 
-  // The Mojo EDK must be initialized before using IPC.
-  mojo::edk::Init();
+  // In some cases, Mojo has already been initialized, so we need to avoid
+  // double-initializing it.
+  if (initialize_mojo) {
+    // The Mojo EDK must be initialized before using IPC.
+    mojo::edk::Init();
+  }
 
   g_shutdown_event =
       new base::WaitableEvent(base::WaitableEvent::ResetPolicy::MANUAL,