Add INTERNAL annotation to namespaces in IDL

tools/json_schema_compiler/test/idl_basics.idl

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Tests a variety of basic API definition features.
 
-namespace idl_basics {
+[internal] namespace idl_basics {
   // Enum description
   enum EnumType {
     name1,
     name2
   };
 
   dictionary MyType1 {
     // This comment tests "double-quotes".
     [legalValues=(1,2)] long x;
     DOMString y;
@@ skipping 42 matching lines @@
     [nocompile] static void function15(long switch);
   };
 
   interface Events {
     static void onFoo1();
     static void onFoo2(long x);
     static void onFoo2(MyType1 arg);
     static void onFoo3(EnumType type);
   };
 };