[NaCl SDK]: Docs -- fix typo in nacl manifest specification (missing "portable")

native_client_sdk/src/doc/reference/nacl-manifest-format.rst

 ###################################
 Native Client Manifest (nmf) Format
 ###################################
 
 .. contents::
   :local:
   :backlinks: none
   :depth: 2
 
 Overview
@@ skipping 38 matching lines @@
 and its dynamic libraries.  See the :ref:`semantics <nmf_url_resolution>`
 section for the rules on URL resolution.
 
 Example of a ``program`` for Portable Native Client:
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 .. naclcode::
 
   {
     "program": {
-      "pnacl-translate": {
-        // url is required
-        "url": "url_to_my_pexe",
+      "portable": {
+        // Required
+        "pnacl-translate": {
+          // url is required
+          "url": "url_to_my_pexe",
 
-        // optlevel is optional
-        "optlevel": 2
-      },
-      // pnacl-debug is optional
-      "pnacl-debug": {
-        // url is required
-        "url": "url_to_my_bitcode_bc",
+          // optlevel is optional
+          "optlevel": 2
+        },
+        // pnacl-debug is optional
+        "pnacl-debug": {
+          // url is required
+          "url": "url_to_my_bitcode_bc",
 
-        // optlevel is optional
-        "optlevel": 0
+          // optlevel is optional
+          "optlevel": 0
+        }
       }
     }
   }
 
 Portable Native Client applications can also specify an ``optlevel`` field.
 The ``optlevel`` field is an optimization level *hint*, which is a number
 (zero and higher). Higher numbers indicate more optimization effort.
 Setting a higher optimization level will improve the application's
 performance, but it will also slow down the first load experience.
 The default is ``optlevel`` is currently ``2``, and values higher
@@ skipping 179 matching lines @@
 required to load the Native Client application.
 
 .. _nmf_url_resolution:
 
 URL resolution
 --------------
 
 All URLs contained in a manifest are resolved relative to the URL of
 the manifest. If the manifest was specified as a data URI, the URLs must
 all be absolute.