Add a 'NACL' plugin type to PepperMessageFilter so we can block private APIs.

content/browser/renderer_host/pepper/pepper_message_filter.cc

Index: content/browser/renderer_host/pepper/pepper_message_filter.cc
===================================================================
--- content/browser/renderer_host/pepper/pepper_message_filter.cc	(revision 165369)
+++ content/browser/renderer_host/pepper/pepper_message_filter.cc	(working copy)
@@ -110,7 +110,7 @@
       host_resolver_(host_resolver),
       next_socket_id_(1),
       incognito_(false) {
-  DCHECK(type == PLUGIN);
+  DCHECK(type == PLUGIN || type == NACL);
   DCHECK(host_resolver);
 }
 
@@ -812,7 +812,7 @@
 bool PepperMessageFilter::CanUseSocketAPIs(int32 render_id) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
   if (process_type_ == PLUGIN) {
-    // Always allow socket APIs for out-process plugins.
+    // Always allow socket APIs for out-process plugins (except NACL).
     return true;
   }