IDL: Avoid generating empty ConstantConfiguration arrays

Source/bindings/tests/idls/TestInterface2.idl

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 22 matching lines @@
 // operations, which need a separate interface to test on.
 // The more *minor* extended attribute should be put in this file.
 
 [
     Constructor, // Test interaction with [Custom=Wrap]
     Custom=Wrap, // Conflicts with and [Custom=ToV8], respectively
     DependentLifetime, // Covered by [ActiveDOMObject]
     SetWrapperReferenceFrom=ownerNode, // Conflicts with [SetWrapperReferenceTo]
     SpecialWrapFor=(TestInterface,TestInterfaceEmpty), // Conflicts with [Custom=ToV8]
 ] interface TestInterface2 {
+    // This interface has only runtime enabled constants.
+    [RuntimeEnabled=FeatureName] const unsigned short CONST_VALUE_1 = 1;
+
     // Indexed property operations with an identifier
     [RaisesException] getter TestInterfaceEmpty item(unsigned long index);
     [RaisesException] setter DOMString setItem(unsigned long index, DOMString value);
     [RaisesException] deleter boolean deleteItem(unsigned long index);
 
     // Named property operations with an identifier
     [RaisesException] getter TestInterfaceEmpty namedItem(DOMString name);
     [RaisesException] setter DOMString setNamedItem(DOMString name, DOMString value);
     [RaisesException] deleter boolean deleteNamedItem(DOMString name);
 
     stringifier DOMString stringifierMethod();
 };