Add an IPC channel between the NaCl loader process and the renderer.

ppapi/c/private/ppb_nacl_private.h

Index: ppapi/c/private/ppb_nacl_private.h
===================================================================
--- ppapi/c/private/ppb_nacl_private.h	(revision 143480)
+++ ppapi/c/private/ppb_nacl_private.h	(working copy)
@@ -15,17 +15,21 @@
 struct PPB_NaCl_Private {
   // This function launches NaCl's sel_ldr process.  On success, the function
   // returns true, otherwise it returns false.  When it returns true, it will
-  // write |socket_count| nacl::Handles to imc_handles.  Unless
+  // write |socket_count| nacl::Handles to imc_handles. |ipc_channel_handle|
+  // will point to information needed to start the IPC proxy.  Unless
   // EnableBackgroundSelLdrLaunch is called, this method must be invoked from
   // the main thread.
   PP_Bool (*LaunchSelLdr)(PP_Instance instance,
                           const char* alleged_url,
                           int socket_count,
-                          void* imc_handles);
+                          void* imc_handles,
+                          void** ipc_channel_handle);
 
   // This function starts the PPAPI proxy so the nexe can communicate with the
-  // browser's renderer process.
-  PP_Bool (*StartPpapiProxy)(PP_Instance instance);
+  // browser's renderer process. |ipc_channel_handle| is the pointer returned
+  // by the call to LaunchSelLdr.
+  PP_Bool (*StartPpapiProxy)(PP_Instance instance,
+                             void* ipc_channel_handle);
 
   // On POSIX systems, this function returns the file descriptor of
   // /dev/urandom.  On non-POSIX systems, this function returns 0.