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 c7b818dd11ad4e392186fc86ba7dc62444003e1c..66521e306370b98eb2e22fd9e30a9072a537ebb5 100644
--- a/ppapi/nacl_irt/plugin_startup.cc
+++ b/ppapi/nacl_irt/plugin_startup.cc
@@ -59,13 +59,17 @@ void SetIPCFileDescriptors(
   g_manifest_service_fd = manifest_service_fd;
 }
 
-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,