Use ChannelMojo from the browser to NaCl loader process.

ppapi/nacl_irt/irt_start.cc

Index: ppapi/nacl_irt/irt_start.cc
diff --git a/ppapi/nacl_irt/irt_start.cc b/ppapi/nacl_irt/irt_start.cc
index b0f09df701bb493bef0437d8703864e2637ce057..e5a62c5330d6cfc94239bbed6ed14ae6e0993c18 100644
--- a/ppapi/nacl_irt/irt_start.cc
+++ b/ppapi/nacl_irt/irt_start.cc
@@ -28,7 +28,7 @@ void nacl_irt_start(uint32_t* info) {
       NACL_CHROME_DESC_BASE,
       NACL_CHROME_DESC_BASE + 1,
       NACL_CHROME_DESC_BASE + 2);
-  ppapi::StartUpPlugin();
+  ppapi::StartUpPlugin(true);

[Mark Seaborn, 2016/07/08 18:22:25]

Instead of parameterising whether ppapi::StartUpPlugin() calls
mojo::edk::Init(), how about just calling mojo::edk::Init() here?  That would be
clearer.

[Anand Mistry (off Chromium), 2016/07/12 07:26:23]

It's not in this CL because it's not necessary yet, but there's more to this
than just calling mojo::edk::Init(). We also need to initialize Mojo's internal
task runner using the IO thread created by StartUpPlugin(). But that's for a
follow-up.

[Mark Seaborn, 2016/09/01 18:43:31]

I see.  I'd still prefer if you didn't parameterise this function in this CL. 
Would you mind keeping the code simpler/clearer for now, and leave the extra
complexity for later changes when it becomes necessary?

[Sam McNally, 2016/09/02 04:42:10]

Done in https://codereview.chromium.org/2305913002/.

 
   nacl_irt_enter_user_code(info, chrome_irt_query);
 }