Use Mojo pipes to signal sync IPC events

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 369b2b7c3487f3ee983427d964c5d149eea6ad0a..c7b818dd11ad4e392186fc86ba7dc62444003e1c 100644
--- a/ppapi/nacl_irt/plugin_startup.cc
+++ b/ppapi/nacl_irt/plugin_startup.cc
@@ -12,6 +12,7 @@
 #include "base/synchronization/waitable_event.h"
 #include "base/threading/thread.h"
 #include "ipc/ipc_channel_handle.h"
+#include "mojo/edk/embedder/embedder.h"
 #include "ppapi/nacl_irt/manifest_service.h"
 #include "ppapi/shared_impl/ppb_audio_shared.h"
 
@@ -63,6 +64,9 @@ void StartUpPlugin() {
   DCHECK(!g_shutdown_event);
   DCHECK(!g_io_thread);
 
+  // The Mojo EDK must be initialized before using IPC.
+  mojo::edk::Init();
+
   g_shutdown_event =
       new base::WaitableEvent(base::WaitableEvent::ResetPolicy::MANUAL,
                               base::WaitableEvent::InitialState::NOT_SIGNALED);