Switch the downloads API over to IDL/json_schema_compiler

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 {
+  // Enum description
   enum EnumType {
     name1,
     name2
   };
 
   dictionary MyType1 {
-    long x; // This comment tests "double-quotes".
+    // This comment tests "double-quotes".
+    [legalValues=(1,2)] long x;
     DOMString y;
   };
 
   dictionary MyType2 {
     DOMString x;
   };
 
   callback Callback1 = void();
   callback Callback2 = void(long x);
   callback Callback3 = void(MyType1 arg);
@@ skipping 33 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);
   };
 };